The wearing of the die is an important factor to the computer-controlled optical surfacing(CCOS). But in actual work

process can not be interrupted to adjust the zero and the wearing of the polishing head can not be compensated on real-time. So an exponential function is put forward to compensate the wearing of the head. The Preston function is modified according to this theory. The constant of the function is also determined by our experiment. This method is introduced into the polish process and the materials' error correction. With this method

the ratio of precision of the CCOS is improved.