Abstract: Low porosity extra low permeability B6 block need be fractured before putting into production. This paper establishes a numerical simulation model when taking into consideration of the start-up pressure and permeability sensitivity to pressure in low permeability reservoir. Using the model, firstly fracture length and conductivity of every stage of horizontal wells and vertical wells are optimized, and then the integral fracturing cases are optimized using orthogonal experimental design and fuzzy recognition method. The optimization results show that the fracture length of stage near the heel and toe should be longer than that of stage in the middle of the horizontal section. The integral fracturing cases are used to direct the fracturing treatment design, and the oil production of horizontal wells is 3.4 times as that of vertical wells, The model is reasonable through comparing the oil production between the model and real data.