Cyclic waterflooding is a kind of waterflood technique, which can improve the waterflood efficiency in low-permeability and fracture-porosity reservoir by changing periodically injected water volume, this article gives the principle and the applied conditions of cyclic waterflooding,and analyses the factors that affect the effect of cyclic waterflooding detailedly, analyzes in detail factors affecting cyclic water-flooding effectiveness.The folluwing conclusions,are drawn:the earlier the cyclic waterflooding process, the better the effectiveness, but the optimal time should be detcrmined by numerical simulations;the longer the cy-clc of the process.the less the permeability;the shorter the cycle. the less the formation elasticity;the betterthe effects, the less the pay zone uniformity;the effectiveness will be the best at proper capillary force.If the ratio of vertical permeability to horizontal one is 0.5, the process effects will be the best;Carrying out nonsym-metrical injection-production process and oil production in turn will get the best cyclic waterflooding effects.