A new scheme of generating the controllable triple-well optical trap is proposed, in which a liquid-crystal spatial light modulator (SLM) is used to fabricate the phase-type blazed grating and be illuminated with coherent monochromatic light. Three optical wells, each of which has the same intensity distribution, can be formed with relative position of the distribution of an equilateral triangle. The relative positions of the optical wells can be changed by simply and conveniently adjusting the phase distribution of the SLM to realize the evolution and reverse evolution from triple or dual wells to single well. The phase grating is designed by simulation according to the technical parameters of the SLM, and illuminated by the laser with ordinary power. The intensity distributions and intensity changes in the adjustment process for the triple wells are calculated. Results show that the controllable triple-well optical trap with very high peak value of intensity and intensity gradient can be obtained. It has many important applications in the experimental study of atomic and molecular optics.