Steady state visual evoked potential (SSVEP) is widely used in the study of brain perception and cognition. At present, the mechanism of SSVEP subharmonic is ambiguous. The induced factors and power variation of the SSVEP subharmonics is studied by a visual cortex network model in this paper. Further, the SSVEP of 20 subjects’ head surface is tested to verify the simulation results. The simulation and experimental results show that the stimulus frequency, stimulus intensity and noise intensity are three important parameters that affect the 1/2 subharmonic induction and power change of SSVEP. Subharmonic is induced by the synergistic action of three parameters: (1) when the stimulus frequency and noise intensity are same, the curve of 1/2 subharmonic power with stimulus intensity is similar to sigma function, and there are non-induction region, linear growth region and saturation region: in non-induction region, 1/2 subharmonic power is approximately 0; in linear growth region, 1/2 subharmonic power is proportional to stimulus intensity; in saturation region, 1/2 subharmonic power is proportional to stimulus intensity; when the noise intensity is same, the stimulus parameters area that can induce the 1/2 subharmonic obviously is similar with arnold tongue in nonlinear synchronization, that is, the effective stimulus frequency range widen with the increase of stimulus intensity; (3) when the stimulus parameter is same, the noise intensity determines the 1/2 subharmonic energy ; the higher the noise intensity is, the stronger restraining effect of inducing 1/2 subharmonic and power is. The experiment and simulation results in this paper are basically consistent, which shows the feasibility of model simulation. The research results provide theoretical and experimental basis for understanding the generation mechanism and effective application of SSVEP subharmonics.