To solve the problem that the collimating lens in the existing dot array structured light projector will result in dramatical zero-order diffraction and uneven intensity distribution of the projected dot, an on-chip dot array structured light projector based on bottom-emitting vertical-cavity surface-emitting laser was proposed as well as the design of the corresponding diffractive optical element. In the design, the target intensity distribution was firstly modified with intensity adjustment and coordinate transformation. Then, the improved Gerchberg-Saxton algorithm based on the Rayleigh-Sommerfeld diffraction integral was applied to obtain the phase distribution of the on-chip diffractive optical element of the projector without collimating lens. Eventually, evaluations of the projected dot was conducted. Simulation results show that the projector can suppress the zero-order diffraction better and obtain more uniformly-distributed intensity when the gaussian beam is used as the light source. In addition, the structure can omit the installation of the collimating lens, thus, reducing the size of the projector and realizing the integration of the light source and the diffractive optical element through chip manufacturing process.