I had to uninstall and reinstall avast because I had a message that say “avast service stopped” and I look online and it say that I need to uninstall and reinstall.
after I finish my flash won’t work on my internet or on my computer like google gadget.
I try to uninstall flash and reinstall but it did not work and also I check for manage add on for internet it is enable.
I don’t know what else to do
Welcome to the forums, zhouzhaoxu 
You may not have had to uninstall/reinstall avast. The first thing to try when you have an avast functioning problem is a repair of avast. You do not say what OS you are using but the below is for XP. Other Windows OS will be similar.
To do a repair of avast :
Control panel > Add/remove programs > click once on avast to select it > click on Change/Remove > scroll down the left pane and click on repair > click OK > follow directions
You can try that now though I am not sure it will help … but it will not hurt to try.
If you still have a problem after, please post in this thread again.
I try that and it won’t let me repair or update but I got it fix
Welcome to the forums zhouzhaoxu.
How did you fix it ?
Yes, please let us know how you fixed it.