In this paper, we study the Cauchy problem of a coupled Cahn-Hilliard system. First, we construct the local classical solution, then by some a priori estimates, we extend the local solution step by step to all t>0 provided that ‖ϕ0‖W1,1(RN)+‖ψ0‖L1(RN) sufficiently small. Finally, based on the Fourier splitting method and the time-independent L1-a priori estimate, we show the temporal decay estimates of the global solution.