The volcanic rocks in the Manitu Formation from the Qilibin area, northern Great Xingan Range are mainly composed of trachyandesite and trachyte. Zircon U- Pb dating results show that they formed during the Early Cretaceous with an age of 142. 2~141 Ma. The geochemical characteristics indicate that the volcanic rocks in the Manitu Formation from the Qilibin area are high in SiO2 (54. 09%~64. 89%), Al2O3(14. 67%~17. 27%)and low in MgO (0. 81%~2. 71%), total alkaline K2O+Na2O (6. 33%~8. 74%), and Mg# (24. 84~46. 15), belonging to the calc- alkaline series with high K contents. The rare earth elements analysis show that the total rare earth elements (∑REE) are in the range of 146. 51×10-6~193. 29×10-6 with insignificant negative Eu anomalies (δEu=0. 64~0. 96), and intense fractionation between LREE and HREE ((La/Yb)N=8. 5~15. 52). The trace elements are characterized by LILE (e. g. 〖KG-*2/3〗, Rb, Ba, K) and LREE enrichment and HFSE (e. g. 〖KG-*2/3〗, Ta, Nb, Ti, Zr, P) depletion, and containpositive 〖JP2〗Hf anomalies, high ratios of Th/Ta, Th/Nb, low ratios of Lu/Yb〖JP〗 (0. 14~0. 16) and Rb/Sr (0. 02~0. 17). Combining their geochemical characteristics with previous studies of this area, the magma for the volcanic rocks in the Manitu Formation from the Qilibin area was derived from the partial melting of the subduction fluid metasomatized mantle wedge, and experienced fractional crystallization and contaminations of crust during the magma ascent. It is possible that these volcanic rocks in the Qilibin area were formed by the collision- postorogenic extension of the Mongolia- Okhotsc Ocean and the upwelling of asthenosphere.