Abstract: From 1:200000 regional geological reports over the years, we have colle- cted about 1216 analytical values of sillicats. According to the relatire regula- tion and demand, we calculated ’the average chemical composition of igneous rcoke in An Hui’ in accorndance with 497 values selected from 1216 analytical values. By using the Added Average Method of sample Number, we have found out the avgrage chemical composition of 51 sorts of rocks, 5 basic types of igneous rocks, intrusive rocks, subvolcanic rock as wellas volcanic rock. On the basis of this work, we have, finally, obtained ’the Average Chemical composi- tion of igneous rocks in An Hui’. According to various sorths of relative ave- rage of oxides and indexes of rock chemistry. Then we expounded several rock chemical characteristics of igneous rocks in An Hui. Eventually, according to the average values of the basic types of igneous rocks and the relative for mulas. We obtained ’the average contents of the main elements of the basic sorts of igneous rocks in An Hui.