My PC is install 360.Can you install avast?avast To work with 360?
As others have said, the general recommendation is that 2 active antivirus programs should not be installed together.
Having said that, Qihoo say that they have designed "360 Total Security" to be compatible with other AV products and I know of a number of installations where this advice has been taken seriously and 360 is installed alongside Avast with no apparent issues.
I have been testing the 2 together on a PC of my own, but only with a specific configuration as follows.
Avast 2015.10.0.2208 -
Custom Install,
Mail Shield only.
Qihoo 360 TS 6.0.0.1124 - Standard install - Protection setting "Balanced" (default)