Abstract: The Ansai Chang 6 ultra-low permeability reservoir has been developed for many years. The front edge of water flooding has swept the high permeability reservoir zone, and a large amount of remaining oil was distributed in the longitudinal low permeability zones of this reservoir. In order to tap the remaining oil in the low-permeability zone, a fixed-plane perforating and fracturing technology was put forward to form a fan-shaped stress concentration plane perpendicular to the wellbore axis, guide the radial extension of hydraulic fractures along the wellbore and control the longitudinal extension of the fractures, so as to tap the potential of remaining oil in the low permeability zone. Based on the studies of remaining oil distribution and the variation characteristics of rock mechanics parameters under long-term injection and production conditions. Then, the effect of fracture initiation under different fixed-plane perforating phases was simulated and analyzed, and the optimized the perforating phase angle according to the size of fractures fusion area. At the same time, the parameters of fracturing stimulation were optimized according to the results of fracture simulation under weak stress difference, by which the fracture height was controlled effectively. The fixed-plane perforating and fracturing technology was applied in 78 wells of the Ansai Chang 6 reservoir. The average daily oil increase per single well was 1.8 t/d after the stimulation, about twice higher than that of the conventional fracturing technologies, with the good results. The research and application of fixed-plane perforating and fracturing technology has provided a new technical means for tapping the potential of remaining oil in low-permeability zone of ultra-low permeability reservoirs.