Abstract: China’s tight oil resources are rich in reserves and have huge economic value, but it is difficult to develop due to the features of low permeability and low porosity of tight oil reservoirs. The spontaneous imbibition principle based on capillary pressure becomes an effective production mechanism for such reservoirs. Combining with nuclear magnetic resonance(NMR) experiments, the paper clarifies the spontaneous imbibition flow law of fluids in tight core, studies the influences of core permeability, core length and one-way imbibition on the recovery percent of spontaneous imbibition based on T2 spectrum and imaging maps obtained from the nuclear magnetic experiment, and observes 2D fluid flowing and distribution in the core. The comparison result shows that the recovery percent of spontaneous imbibition obtained from T2 spectrum is consistent with that obtained from the mass method, which verifies the applicability using NMR experiments to study tight reservoir spontaneous imbibition and provides a reliable theoretical basis for tight oil development