Located at the juncture of Zhejiang and Fujian, the Yaokeng granite mass which intruded into the lower part of Early Cretaceous Shimaoshan Group lies in the northern side of Mazhan town of Cangnan County. This paper has conducted a detalied mineralogical, petrological and geochemical studies on this rock mass and discussed its petrogenetic type. Investigation results show that granites at Yaokeng develop typical micrographic texture and miarolitic structure,and are composed mainly of quartz (>30%), perthite (65%±), and minor arfvedsonite (2% ~3%) and biotite (1%±). Accessory minerals in these rocks include fluorite, zircon, allanite and Ti-Fe oxides. Chemically, the Yaokeng granites are rich in silica (SiO2=77.13%~77.82%) and alkali (K2O+Na2O=7.99%~8.48%), with (K2O+Na2O)/Al2O3(moecular ratio) values ranging from 0.96 to 1.02. They also have high differentiation indices (DI= 95.5~98.2) and oxidation ratios [Fe2O3/(Fe2O3+FeO)=0.56~0.96]. They are also rich in Rb, Th, Ga, LREE, Nb, Zr, Hf, with (Ga/Al)×104values equal to 3.53~3.95, poor in Sr, Ba, Cr, Co, Ni, V, and show intensive europium depletion (δEu=0.22~0.25). These features are quite similar to thoes of the typical alkali granites. Based on an integrated analysis of the geological and geochemical characteristics of Yaokeng granites, and a systematic comparison of them with Kuiqi and Taohuadao granites, this paper concludes that the Yaokeng rock mass is also a typical postorogenic alkali granite occurring in late Mesozoic magmatic belt along the coastal area of Zhejiang and Fujian Provinces.