Tight volcanic reservoirs, characterized by strong heterogeneity and a well-developed fracture network, are usually difficult to develop. The development of effective ways to enhance production in such reservoirs is an important task in research work for oil and gas field development. The method of enhancing production by imbibition is a promising technology for oil recovery in tight reservoirs. In this paper, based on the production data of horizontal wells in tight volcanic reservoirs, we have studied the imbibition mechanism during fracturing fluid flowback. Nuclear magnetic resonance (NMR) technology was used for analysis. First, the wire-cutting technique was used to simulate fractures generated by hydraulic fracturing in the core. Then the core was filled with quartz sand. Then the migration of fluid between small pores and macropores during the imbibition process was studied by low-field NMR analysis. The research results show that the imbibition displacement of fracturing fluid under high pressure can effectively increase the recovery rate, while the soaking time can affect the imbibition exchange of fluid between crack and matrix. Due to the small pore radius and high capillary resistance of the volcanic rock, the imbibition stability time is longer. The pore size distribution of volcanic rock was analyzed quantitatively by NMR and mercury intrusion porosimetry. The results show that the dynamic imbibition process occurs mainly in pores less than 2 im.