Why battery drain even after replace it?

Your best place to start would definitely be to check the battery usage statistics under Usage in Battery Manager in Settings. This should allow you to see if there's an exorbitant background apps or processes taking up unreasonable amount of battery life or any other potential software/processing issue.

I can't pinpoint exactly where your issue may lie, but here's some general tips for getting the most out of your battery.

• Keep your phone out of high temperature situations as this greatly damages your battery and phones innards, cooler is almost always better!
• Avoid keeping your phone at 100% battery
• The safest place for your phone to be charge wise is between 40 and 80 percent for giving your battery a long life
• Avoid using third party chargers, even common car chargers may be more harmful to your phone's battery than the convenience they provide
• Close out any unnecessary apps when you're done using them and dim your phone's brightness to elongate your battery life

I hope this information can be of some use to you!