The long drilling period and insufficient reservoir reconstruction scale are the main factors restricting the economic and effective development of natural gas in Fuxian block. By simplifying the casing program of horizontal wells, the drilling period can be greatly shortened and the large-scale reservoir reconstruction can be realized. Based on the actual drilling formation data, through theoretical analysis and numerical simulation, it is clear that mudstone is easy to lose stability, there exists difficulty on long open hole cementing, and there is the problem of salt water invasion and poor reservoir protection. It is necessary to optimize the design of secondary casing program scheme of horizontal wells, support the well wall stability technology, and formulate the casing program transformation plan, etc. The application results show that the design scheme can ensure the smooth implementation of the secondary casing program of the horizontal wells in Fuxian block, shorten the drilling cycle, and provide more safe and effective borehole conditions for the later transformation.