Abstract: Different from the traditional fast neutron imaging system, the use of associated particle imaging technique can eliminate the interference of most γ-rays and scattered neutrons without mechanical collimators, and make it possible to perform fast neutron imaging of thick and heavy objects with excellent contrast. Angular resolution is an important parameter that affects the system performance. Through theoretical analysis, the effects of the incident ion initial momentum, target spot size and detector spatial resolution on the system angular resolution were studied. The two-dimensional images of neutron emission angle distribution under different parameters were calculated using the GEANT4 simulation program. The analysis and simulation results indicate that the target spot size and spatial resolution of α detector are important factors that affect the angular resolution. To obtain a system angular resolution of less than 1°, the initial momentum variation range of incident ions should be small, the target spot diameter should be less than 1 mm, and the spatial resolution of the α detector should be less than 0.5 mm.