Official figures have shown a total of 72.4% of red calls were reached within eight minutes in December.
It follows a new year-long pilot to test changes to the Welsh Ambulance Services NHS Trust's patient response.
In November, nearly 71% of code red calls were responded to compared with the 65% target.
The new pilot, implemented in October, measures the results of treatment and patients' overall experience in a bid to make sure they receive the most appropriate care.
The Emergency Ambulance Services Committee, which oversees the compilation of the data, said Wales now has the most detailed information on ambulance performance across the UK.
The new data, for October to December, showed that out of 69,686 patients taken to hospital or another destination by ambulance, the vast majority - 63,694 - went to A&E.
Ambulance crew handed over 58.2% of cases to hospital staff within the target time of 15 minutes, yet 12,233 hours were lost due to delays.
Since a new traffic light system for grading calls was introduced, call centre staff have been given more time to determine the nature of the emergency.
Of the total number of emergency calls received in December, 1,927 (5.0%) were red - "immediately life threatening" - the figures showed.
Of those, more than 90% of red calls received a response within 15 minutes, but seven responses took longer than 30 minutes to arrive.
Amber calls, deemed serious but not life threatening, do not have a target time but 65% were responded to within 15 minutes and 23 seconds.
Emergency response time figures for November cannot be compared to December's as revised changes where introduced on 11 November, meaning a 999 call is now upgraded to a red category if the patient deteriorates.
Tracy Myhill, chief executive of the Welsh Ambulance Service, said they were "committed to learning and improving from this pilot as we move forward".
Deputy health minister Vaughan Gething said it was "encouraging" to see "continuing improvement".
"The new clinical response model is helping to ensure people get the right care, in the right place, at the right time," he said.
However, he called for improvements in Powys and Hywel Dda health boards' performances, as both failed to reach the 65% emergency response target.
Welsh Liberal Democrats leader Kirsty Williams has criticised the variation in response times across Wales, adding: "Labour ministers need to address this imbalance quickly."

The Vikings are top of the table with five wins from their opening six games and next face Wigan on Thursday.
"You've got to be on your game and the lads and coaches are working hard to prepare and are reviewing how we can get better," Betts said.
"It's how we train and carry ourselves, those things don't just turn up."
Since regaining their Super League license in 2012, Widnes have failed to finish in the top half of the table.
Last season they went through the Qualifiers to retain their top-flight status, but Betts says they are better equipped to succeed this season.
"Working hard and making it happen week in week out, that's a skill and it's something that we've not been able to do throughout the last three years," Betts told BBC Radio Merseyside.
"We've got some distinctive, confident players so we've scored some points and passed the ball really well and asked some questions."
Media playback is not supported on this device
After Widnes thrashed Hull FC 46-6 last week, Betts admits he is finding it difficult to rotate his squad with his side performing so well.
"The tough thing at the moment is we've got three or four lads who you want to try and give some game time to, like Paddy Flynn, Pat Ah Van and Tom Gilmore," he added.
"It's hard to get Tom into the game and I know I'm going to have to use him. I need him fit and need him to get some game time, but it's hard when the half-back pair is playing as well as it is."
New data measuring how effectively ambulance staff in Wales deal with 999 calls has been published for the first time.
[NEXT_CONCEPT]
Widnes Vikings boss Denis Betts says their strong start to the Super League season is a reflection of their meticulous work in training.