Bicycle Tutor

After maintaining the Bottom Bracket, I found that it is loosing. Do you know what will result in? Should I change the bearings or the whole BB?

OK, are you saying that you overhauled your bottom bracket and that it is still loose?
If so, you can see in Alex's tutorial on the bottom bracket that you need to make a few adjustments if it is still loose after you've serviced it.

The decision to change the bearings mainly comes down to the condition of the races. If the surface where the bearing rotate on the axle/spindle and in the two cups looked smooth and shiny, they're probably fine. If it was rough or pitted, you should replace the pitted parts and the ball bearings.
If the BB is coming loose after you've installed and adjusted it, you probably didn't get the fixed cup tight into the frame or didn't get the lock ring down tight enough. Make sure to not to over tighten the adjusting cup, but the lock ring needs to be snug.