The invention provides an injection increasing method for water-injection development of an oil reservoir. The injection increasing method comprises the following steps that (1) according to the reservoir characteristics of to-be-killed wells, a fracturing technology is optimized; (2) water source water samples and resistance reducing agents nearby a to-be-killed well field are taken for compatibility performance test, and if compatibility performance is good, a mixed solution of anti-swelling agents, the resistance reducing agents and the water source water samples is subjected to a core damage experiment and an anti-swelling performance experiment; (3) according to the well set deficit amount, the injected liquid amount is optimized; (4) the expected construction pressure is calculated,and the liquid inlet mode is selected; (5) on-site construction is conducted, adjacent wells in the same well set are all shut in, and a pressure gauge is mounted; and (6) according to the well set pressure change, the water sample analysis result and/or the core test result, the well shut-in time is determined, and the oil well opening sequence is optimized. According to the injection increasingmethod for water-injection development of the oil reservoir, fracturing and energy-increasing water injection are combined so that the problems that an existing low-permeability oil reservoir is poorin water-injection effect, consequently, formation energy cannot be effectively supplemented in time, and the oil well yield is lowered rapidly can be effectively solved.