hey i have a problem with avast, when i installing a game, avast alert that part of that game is a trojan, but i really know that that file isn’t a trojan so i use avast exclusion on avast setting, but when i want play that game, avast alert still appear, so i must disable avast if i want to play that game. 
so please help me how to exclude this part of game so avast alert doesn’t appear again and i can play this game, i don’t want uninstall avast because i very like avast 
The only way to really know it isn’t infected is to confirm or deny the detection.
You could also check the offending/suspect file at: VirusTotal - Multi engine on-line virus scanner and report the findings here. You can’t do this with the file securely in the chest, you need to extract it to a temporary (not original) location first, see below.
Create a folder called Suspect in the C:\ drive, e.g. C:\Suspect. Now exclude that folder in the Standard Shield, Customize, Advanced, Add, type (or copy and paste) C:\Suspect* That will stop the standard shield scanning any file you put in that folder. You should now be able to export any file in the chest to this folder and upload it to VirusTotal without avast alerting.
If it is indeed a false positive, see http://forum.avast.com/index.php?topic=34950.msg293451#msg293451, how to report it to avast! and what to do to exclude them until the problem is corrected.
Whilst this might seem a pain in the rear it really is the correct way to deal with a false detection, so you don’t treat the symptom (the alert) treat the problem, mis-detection. So when it is corrected it not only helps you but other avast users who might also use that game.
Which is the game, by the way?