Abstract: Impregnated diamond bit has been applied extensively to the fields of geo drilling,stone processing,etc.However,some problems about the relationship between bit performance and diamond parameters need to be studied further.In this papaer,the distributing model of diamonds on bit crown is obtained through theoretical calculation and its result is well fit to the real distribution of diamonds.Based on the model,the effect of diamond size on the performance of diamond bit is discussed.The conclusions are helpful to the design of deamond bit.