Abstract: According to the cross -filtration theory of formation elasticity-capillary force for cyclic waterflooding and on the basis of input -output balance principles, a formula is derived for evaluating the feasibility of cyclic waterflooding in waterflooding oilfields by using geologic models and by combining the corresponding parameters with numerical models, reservoir engineering, economic evaluation and mathematical statistics. Four types of factors influencing the effects of cyclic waterflooding are considered in the formula including reservoir parameters, development parameters, cyclic waterflooding parameters and economic parameters.