Abstract: Physical nature of reservoir space of fracture reservoir is complex and specified, imbibition effects controls water flooding effects, and the pulse imbibition displacement has always been considered as an effective development mode of low-permeability fractured reservoirs. On the basis of indoor experiment, theoretical knowledge of reservoir engineering has been used to study the pulse imbibition displacement mechanism and results show that changing the condition of imbibition by pulse pressurization is the ultimate reason of enhanced imbibition displacement effectiveness using the pulse water flooding.