i have notice it stop working when i press alt key 5times..
There is no "alt" key on the Mac. You are talking about the Option (symbol ⌥) key (which also bears the label "Alt" for use with emulators or non-Mac apps).
how can i disable this fuction?
System Preferences > Universal Access > Mouse & Trackpad (or Mouse) > Mouse Keys > Off.
When mouse keys is engaged, some keys are used to control the cursor and other mouse features; other keys are disabled. This feature was designed for users with mechanical disabilities; however, once you understand it, you may discover that it can be very useful with Photoshop, because it allows for fine and precise cursor movements. See