A large number of garnets are developed in the garnet granites in the Wulashan area, Inner Mongolia. As these garnets contain important information about the metamorphic evolution history of the host rock, it is very important to clarify their genetic type. Although the predecessors suggested that it is peritectic garnet, they failed to provide sufficient evidence to prove it. Towards this end, this article has conducted petrographic and mineral chemistry studies on the anatase garnet biotite gneiss and garnet in the garnet granite.The results show that, on the outcrop, from low anatectic garnetbiotite gneiss to garnet granite or veins of moderate anatectic garnetbiotite gneiss, the size of garnet gradually increases. When the veins in the rock are small and few, there are no coarsegrained garnets; when the veins are large and many, the coarsegrained garnets develop in the rock, and a large number of coarsegrained garnets develop in the garnet granite. In addition, the grain size of garnet in the vein is larger than that in the matrix as a whole. On the microscopic features, the garnets in the garnet granite or veins of moderate anatectic garnetbiotite gneiss have poor crystal shape and different shapes, with a jagged boundary. They also have sieve texture, and some have the characteristics of developing at the core but not at the edge. The reverse reaction structure and plagioclase pile crystals can be seen in the matrix of the garnet granite or veins of moderate anatectic garnetbiotite gneiss. In terms of mineral chemistry, the garnets in the garnet or veins of moderate anatectic garnetbiotite gneiss are characterized by rich Fe and Mg and poor Mn and Ca, with no growth zone. The garnet in contact with biotite develops diffusion zones, which shows that the FeOT curve increases from the center to the sides, and the MgO curve decreases from the center to the sides, and the two are negatively correlated. Comprehensive analysis shows that the garnet in the garnet granite grows from solid phase metamorphism to a state of continuous growth in a state where an anatomic melt is encased in the metamorphic anatex process. It is believed that this kind of garnet is the cause of remelting, and it is a remelted mineral phase (equivalent to the residual mineral phase). In addition, the garnets in the veins in the moderate anatectic garnetbiotite gneiss also have the same genesis, indicating that the two are closely related, and provide a strong basis for the garnet granite to be a highly anatectic product of the garnetbiotite gneiss. At the same time, the phenomenon that a large number of transformationtype garnets remain in the granite indicates that the granite in the study area has not undergone longdistance migration to completely separate the solid and liquid phases, which further proves its insitusemisitu origin.