Abstract: For the purpose of deducting the initial common lead of in situ LA-ICP-MS U-Pb isotope dating of cassiterite, this pa-per has discussed the theory, effect, advantages and limitations of concordia and isochron methods and the basic principles for selecting a suitable method in experiment based mainly on the authors' studies, combined with recently reported related references. The results show that the two methods have different advantages and limitations in deducting the initial common lead of in situ LA-ICP-MS UPb isotope dating of cassiterite. In practical work, it is very important to choose an appropriate method according to the age range of cassiterite, total U, Pb content, common lead relative content and dating accuracy requirement of the samples.