Focusing on the application of monofractal and multifractal theory in unconventional reservoir research, the research results on the application of fractal theory in quantitative characterization techniques, digital image techniques and techniques for joint multi-method characterization of full-scale pore structure are reviewed. There are four weaknesses in the existing research results: 1) lack of methodological research on joint multi-method for full-scale fractal geometric characteristics; 2) lack of research on the applicability of different fractal dimension calculation models; 3) lack of research on the control factors of segmental fractal pore size; 4) lack of research on the heterogeneity differences of reservoirs containing multiple types of resources by applying fractal theory. The development direction of the application of fractal theory in unconventional oil and gas reservoirs is proposed. On the one hand, the methodological and applicability research of fractal dimension calculation models should be strengthened, and the controlling factors of segmental fractal pore size should be clarified; on the other hand, more in-depth research should be conducted on the dynamic coupling relationship between hydrocarbon generation and fractal dimension change, and the further application of multiple fractal theory in the study of unconventional reservoirs should be strengthened.