Hello,
i have an  CNC machine from china a year ago and i didnt use it because the motor not moving smooth,
i am thinking to upgrade the controller by connecting arduino to the stepper in the old control box to
controlled by Arduino, i search for long time and i found arduino program which called Grbl and i want
some one to help me and tell me if can connect the arduino with the old control box stepper, and if
there any way to connect it late with Mach3

do a search through this site the information is there you just need to look for it

No, you can't control your motors through an Arduino with Mach3.

no way to do that?
any other help?

Hi Sayed,

My best advice, assuming you want to use Mach3, is to fit a higher quality controller to your machine (such as the Gecko G540 or similar). 
GRBL is OK but extremely limited compared to Mach3 but at the end of the day, the choice is all yours.

Tweakie.