Improving the luminescence collection intensity of diamond NV color center is the key to realize single photon source. A tapered diamond-like carbon (DLC) gradient antireflection film is introduced into a diamond nanocolumn color center single photon source, aiming to improve the luminescence collection intensity of NV color center from the aspects of spontaneous radiation rate and photon collection efficiency of color center. The finite difference time-domain (FDTD) method is used to simulate the composite structure optically, the effects of DLC film with different structural parameters on the photon collection intensity, emission efficiency and spontaneous radiation rate of NV color center of diamond nanopillar are investigated, and the structural parameters at the maximum collection intensity are obtained through optimization. The simulation results show that the introduction of DLC film can make the NV color centers in diamond nanopillars achieve a higher photon emission efficiency (≥1%), change the internal electric field distribution of the nanopillar, increasing the spontaneous radiation rate of color center by 16.8%, and finally increase the total photon collection intensity by 15.5%.