Abstract: According to the national standard of China’s oil and gas industry, the recovery factor is calibrated with the waterflooding characteristic curve for the developed sandstone reservoir based on the water?cut limit of 98%. For reservoirs with over 98% of ultra?high water cut, the calculation method listed in the national standard of China’s oil and gas industry is no longer available. Based on the calculation of water?cut limit for the reservoirs, this paper presents the calibrated recovery factors of the reservoirs with ultra?high watercut in OBJ1 reservoir of KS oilfield in Kazakhstan , by using the oil?water relative permeability curve derived from the A?type waterflooding characteristic curve, generalized Tong’s chart and the production data, as well as the numerical simulation method. The results show that the recovery factors calibrated by the former three methods are very close to, so these methods can be used. Whereas the recovery factor calibrated by thenumerical simulation method is a bit high, and can be used as reference