My macbook pro mid 2012 turn off when i unplug charger Battery information is given below?? What should i do now??

Battery Information:

  Model Information:
  Manufacturer: SMP
  Device Name:  bq20z451
  Pack Lot Code:    0
  PCB Lot Code: 0
  Firmware Version: 201
  Hardware Revision:    000a
  Cell Revision:    165
  Charge Information:
  Charge Remaining (mAh):   4042
  Fully Charged:    Yes
  Charging: No
  Full Charge Capacity (mAh):   4226
  Health Information:
  Cycle Count:  1050
  Condition:    Replace Now
  Battery Installed:    Yes
  Amperage (mA):    0
  Voltage (mV): 12304
You're going to have to replace the battery I'm afraid.

Your battery is gone past it's lifetime and cannot function without a constant power supply.

This can be seen in the message you pasted - "Condition: Replace Now".

You can either buy a new battery and follow a guide to replace it yourself, bring it to a computer repair shop or bring it to an Apple Store.