The Carboniferous System in the Majiaoba area of northwestern Sichuan Province is well exposed, richly fossiliferous and is a classical Carboniferous succession. The authors carried out a microfacies analysis of this succession. The analysis shows that the Lower Carboniferous System in the Majiaoba area represents a transgression-regression-transgression cycle, and the Upper Carboniferous System includes four short-term depositional cycles and two complete transgression-regression depositional cycles.