Abstract: In some respects, angular unconformities in the Precambrian metamorphic terrains are different from those in the Phanerozoic. In the Precambrian metamorphic terrains, as a result of superimposition of polyphase tectonic movements, metamorphism and migmatization, stratification was replaced by schistosity, and unconformable planes were folded with strata; therefore angular unconformities are not easy to recognize. And being tectonic planes of weakness, the planes of unconformity are liable to be intruded by magmas and are also prone to fracturing and displacement. These factors often cover the Precambrian angular unconformities. Under the oxygen-deficient conditions, the Precambrian crust of weathering, unlike the Phanerozoic one, is lacking in red Fe-Mn enrichment zones and white kaolinization zones. Owing to different intensities of weathering and different conditions of transportation and accumulation, basal conglomerates are not necessarily present on the planes of angular unconformity; if any, the composition of the gravels is not necessarily complex either. These factors often keep us from recognizing Precambrian angular unconformities. The loci where the geological processes differ distinctly, e. g. those between different metamorphic belts, different sedimentary formations and different volcanic formations and the structurally discordant areas, are favourable for looking for angular unconformities. In the past it was considered that the places where there were intense facies changes or large-scale overthrust faults were also candidates for looking for angular unconformities. Angular unconformities with indistinct angular discordance between two sets of strata can often be found through tracing the lower boundary of clastic rock series traversing the terrain and short sections. In general, angular unconformities are most easy to find in places where the overlying strata have well-developed stratification and a gentle dip and the vision of field is wide.