Is there any method of preventing someone from using my Mac if stolen(Like icloud activation lock-in iPhone).I heard that FileVault will only prevent stealing data.
There are a couple extra things you can do. First turn on the firmware (EFI) password. This way if someone steals your Mac, even if they take out your FileVault encrypted drive and put in a new drive, the system still will not work... so they will have stolen a worthless Mac that cannot boot.
Second thing is turn on iCloud's Find my Mac. Then if your Mac is stolen, you can login to icloud.com and send a lockdown to the Mac. This will apply a firmware lock similar to the one I mentioned above. The only catch is the theif would need to turn on the Mac and connect it to the Internet for the Mac to receive the lockdown command. Find my Mac can also show you where your stolen Mac is located when it connects.