Staffordshire Police said material relating to the deaths of 214 patients between 2005 and 2009 was reviewed.
Deputy Constable Nicholas Baker said there were "no grounds" for a criminal investigation against any individual clinician or manager at the trust.
He said this did not detract from the "appalling care" many suffered.
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The review was set up in 2013 and led by a panel which included the South Staffordshire Coroner and the Crown Prosecution Service.
Mr Baker said "a direct result of this work" had been two successful criminal prosecutions against Mid Staffordshire NHS Foundation Trust. He said without the review it was "highly unlikely" the trust would have been prosecuted for the deaths of Ivy Bunn, Lillian Tucker and Gillian Astbury.
The now defunct trust was fined Â£500,000 last December for "basic" blunders linked to the deaths of the three elderly women, as well as the death of 89-year-old Patrick Daly in 2014.
Mr Baker said the review had involved an "extensive examination" of material relating to the 214 deaths.
"That there were no grounds to support individual criminal investigations does not detract from the appalling care that many patients suffered during the period of this review; patients and their families were badly let down by the trust, and some of its clinicians and their management," he said.
"We believe the improvements made to the way different agencies work together, the regulatory and reporting framework, and the systems in place to report deaths in healthcare settings to appropriate authorities has strengthened the system considerably since the original tragedy."
Stafford Hospital, which is now County Hospital, was at the centre of a Â£6m public inquiry into care failings. A new NHS trust was set up in 2014 to run the hospital and Royal Stoke University Hospital.
A police-led review into high death rates at the former Stafford Hospital has found there is not enough evidence to prosecute any individuals.