can i delete points which the members earn when they post i don't mean all points i want to delete some ?

Administration Panel > Modules > Points & Reputation > Points Donation
You can add or subtract points from members here.  There is no way to do it for everyone at once.  You will have to manually do each one separately.

How to add or subtract points:

1. Pick a member
   
2. Erase the points in the box
   
3. Enter the new number (Example: member has 100 points.  You want to add 10 points.  Erase the 100 points and enter 110 points.  Or you want to remove 20 points.  Erase the 100 points and enter 80 points.)
   
4. Press the save button

thanks..solved