Mean field approximation is extended to multicomponent stochastic reactiondiffusion systems. A multivariate nonlinear selfconsistent Fokker–Planck equation defining the probability density of the state of the system, which describes a wellknown model of autocatalytic chemical reaction (Brusselator) with spatially correlated multiplicative noise, is obtained. The evolution of probability density and statistical characteristics of the system in the region of Turing bifurcation are studied.