We have synthesized SiO2 particles by Sol-Gel method. By the variation of TEOS and NH4OH concentration we obtained 1,2 and 4 µm size SiO2 particles. During this experiment, microchip electrophoresis can be controlled by the switching the voltage toward the direction of the analyte using buffer K2HPO4 / KH2PO4 ( pH 8.0,0.1 M ) in the channel. According to the result of experiment, by means of time control and voltage is 205V,the sampling time depends on different size of SiO2 particles, which are 1,2 and 4 µm, the sampling are respectively 50、80、110 seconds, the number of particles are 36.7、30.7、20.7. With the method of the most suitable sampling, we discover the best voltage of separation time is 350V, In accordance with the dimension of particles are 1,2 and 4 µm, 3、4、5 mins and to separate 10.3、8.0、6.3 particles.