The zircon grains from the Jiaochong pyroxene diorite pluton in the Tongling area of Anhui Province can be categorized into two types based on the CL images. Type I zircon grains are offwhite, show clear oscillatory zoning, and have relatively low concentrations of U, Th, Pb and REE. All these characteristics indicate their magmatic origin. A weighted average 206Pb/238U age of 1285±21 Ma (MSWD=029) yielded in this study may represent the crystallization age of the pluton in a close environment. Combined with the previous published age data, our result indicates there are two periods of magmatic activity. The age data along with the published age of magmatic rock indicate that the Tongling area not only contains the 145~135 Ma magmatic emplacement activity, but also the 134~123 Ma magma activity, which has not been acknowledged but occurred at the same time as volcanicintrusive rocks in volcanic basins such as the Ningwu basin and Luzong basin. Type II zircon grains are greyish black and show unclear oscillatory zoning, and have extremely high concentrations of U, Th, Pb and REE. The type II zircon grains are called “high U zircon”, and might be influenced by 〖JP2〗hydrothermal process. The weighted average 206Pb/238U〖JP〗 age of 141.4±2.0 Ma (MSWD=1.06) obtained in this study has no definite geological significance. The two types of zircon grains with two groups of ages occuring in the same pluton verify that if we do not distinguish zircon grains when calculating the weighted average UPb age, the results obtained may not be correct or confuse the geological facts. Another significant characteristic of zircon grains from the Jiaochong pyroxene diorite pluton is that the crystal forms of zircon grains are poorly preserved and fragmented, with embayed texture. This indicates that the formation of Jiaochong pluton may have experienced zircon crystallization, corrosion, and the preservation of corrosion morphology. The characteristics of the two types of zircon grains and the UPb age from the Jiaochong pyroxene diorite not only record the earlier crystallization and hydrothermal metasomatism of the intermediateacidic magma, but also reflect the later mafic magma injection and mixing during the diagenetic stage. This reveals the formation of the host rocks has experienced a complicated process: magmatic crystallization SymbolnB@ hydrothermal metasomatism SymbolnB@ magmatic crystallization SymbolnB@ magmatic mixing SymbolnB@ magmatic emplacement.