Based on the analyses of the Brownian motion of two interactive colloidal particles, the experimental method for measuring the interaction potential between two micro-scale colloidal particles was studied by making a micro observation of Brownian motion of particles. The measuring system was constructed by dual optical tweezers and a synchronized chopper. This method was used to measure the interaction potential of a pair of 1μm diameter polystyrene spheres. The consistency between the measured result and the DLVO (Derjagin-Landau-Verwey-Overbeek) theory provides direct microscopic experimental evidence to the theory. Some parameters deciding the experimetal precision and efficiency, such as the switching time, the duration of the on and the off state of the optical tweezers, the distance between the sample particles and the bottom of the sample cell, and the precision of experimental measuring interval, were discussed. The apparatus and method provide an effective technique for measuring the interaction potential between particles of different colloid system and getting an insight into the microscopic foundation for the macroscopic properties of colloids.