According to the theory of orthogonal polynomial, the Hopf bifurcation of fractional-order stochastic Duffing system at zero balance point is studied. Firstly, converting the fractional-order stochastic Duffing system into its equivalent deterministic one by using Laguerre orthogonal polynomial approximation principle. its response is obtained in the numerical calculation. Finally, it can using two lemmas to get the critical value of Hopf bifurcation in equivalent system, and the theoretical analysis results are verified by numerical simulation.