Compared with other nonlinear optical materials, KTP crystal has prominent advantages. But it also has high conductivity and it becomes difficult to efficiently control domain-reversion with conventional method, due to the existence of ionic current. So to conquer the difficulty, it is necessary to monitor the polarization-reversal process of KTP crystal in realtime. Realtime monitoring method into the fabrication of PPKTP, short for KTiOPO4 is carried out by utilizing electrooptical effect. The principle is analyzed theoretically and the result demonstrates the validity of the method experimentally. Compared with the results without the monitoring method, the conversion efficiency of PPKTP crystal increases by many times. It is proved that this method can be used to enhance the quality and repeatability of PPKTP crystal fabrication, and is also effective to examine the quality of PPKTP crystal.