The　complex　pore　structure　of　unconventional　oil　and　gas　reservoirs　is　one　of　the　reasons　for　the　difficulties　in　resource　evaluation　and　development.　Therefore,　it　is　crucial　to　comprehensively　characterize　the　pore　structure,　understand　reservoir　heterogeneity　from　multiple　perspectives,　and　gain　an　in-depth　understanding　of　fluid　migration　and　accumulation　mechanisms.　This　review　outlines　the　methods　and　basic　principles　for　characterizing　microporous　systems　in　unconventional　reservoirs,　summarizes　the　fractal　analysis　corresponding　to　the　different　methods,　sorts　out　the　relationship　between　the　fractals　and　reservoir　macroscopic　physical　properties　(porosity,　permeability,　etc.)　with　the　reservoir　microscopic　pore　structures　(pore　structure　parameters,　pore　connectivity,　etc.).　The　research　focuses　on　cutting-edge　applications　of　characterization　techniques,　such　as　improved　characterization　accuracy,　calibration　of　PSD　ranges,　and　identification　of　different　hydrogen　compositions　in　pore　systems　for　dynamic　assessment　of　unconventional　reservoirs.　Fractal　dimension　analysis　can　effectively　identify　the　quality　level　of　the　reservoir;　complex　pore-throat　structures　reduce　permeability　and　destroy　free　fluid　storage　space,　and　the　saturation　of　removable　fluids　is　negatively　correlated　with　Df.　As　for　the　mineral　composition,　the　fractal　dimension　is　positively　correlated　with　quartz,　negatively　correlated　with　feldspar,　and　weakly　correlated　with　clay　mineral　content.　In　future　qualitative　characterization　studies,　the　application　and　combination　of　contrast　agents,　molecular　dynamics　simulations,　artificial　intelligence　techniques,　and　4D　imaging　techniques　can　effectively　improve　the　spatial　resolution　of　the　images　and　explore　the　adsorption/desorption　of　gases　within　the　pores,　and　also　help　to　reduce　the　computational　cost　of　these　processes;　these　could　also　attempt　to　link　reservoir　characterization　to　research　on　supercritical　carbon　dioxide-enhanced　integrated　shale　gas　recovery,　carbon　geological　sequestration,　and　advanced　underground　hydrogen　storage.