Research on the imbibition mechanism of gel breaking fluid of clean fracturing fluid mainly focuses on macro core wettability，oil-water interfacial tension and core-scale recovery，lacking intuitive and effective understanding of oil-water two-phase migration behavior in micro/nano pores during imbibition. In this paper，the gel breaking fluid of clean fracturing fluid was used as experimental fluid，and the dynamic distribution of oil-water two-phase under capillary force imbibition was simulated by using 2.5-dimensional pore-throat microchannel. The experimental results showed that there were continuously dynamic equilibrium processes between capillary force（driving force）of wetting phase and interfacial expansion，Jamin effect and viscous force loss（resisting force）in the imbibition process of clean fracturing fluid. The oil-water two-phase migration formed an alternate stage process of“water absorption，oil drainage and water absorption”. When the oil production efficiency reached 10.98% ， 19.09% and 37.27%，water absorption and oil drainage alternated to produce oil. It was a similar effect of“suppressing pressure”. The oil-water two-phase migration behavior in micro/nano pores was a great significance for understanding the imbibition mechanism of clean fracturing fluid.