<p>Samples from Chang 8 reservoir in southern Yan ‘an area were taken to conduct experimental studies on the imbition of surfactant GPHQ-1 at different imbibition times to evaluate the imbition effect and influencing factors of the surfactant. The results show that the concentration of surfactant GPHQ-1 is between 0.05% and 0.5%, and with the increase of the concentration of the imbitant, the interfacial tension showed a trend of decreasing first and then increasing. When the concentration of GPHQ-1 is 0.1%, the interfacial tension reaches the minimum. Through core imbibition experimental test at a concentration of 0.1%, the initial imbibition rate reaches 54.50%/h, and the imbition efficiency after 24 can reach 33.06%, which is significantly higher than that of pure water imbition samples. Infiltration mainly occurs in the micro-pore throat and micro-pore throat, and GPHQ-1 can enhance the imfiltration of micro-pore throat and micro-pore throat. With the increase of imbibition time, the imbibition of the mesoporous throat also improves. The imbibing stratified test of GPHQ-1 in rock samples shows that the imbibing efficiency and imbibing rate are negatively correlated with the average pore throat radius. The larger the average pore throat radius, the lower the imbibing efficiency and the lower the imbibing rate. The contribution of pore throat to imbibition efficiency shows obvious differences between the front end and the end of the sample. The closer to the front end of the sample, the greater the imbition efficiency. The contribution of micro pore throats to the imbition effect is greater. The closer to the end of the sample, the fine pore throat and the mesoporous throat contribute more to the imbibition efficiency.</p>