Abstract: Since traditional reserves estimation method cannot make full use of production exploration data and reproduce the distribution of spatial data,they are difficult to give an accurate guidance for subsequent production.This article assumes that Krige is used to calculate reserves firstly,then attempts to import Sequential Gaussian Simulation algorithm which is commonly used in reservoir modeling into the deposit reserves update.A large open-pit molybdenum mine was taken as a case to prove the algorithm,then a model which contains different sizes and classification of reserves was obtained.The result was analyzed from the view of frequency histogram of grade distribution and variation function.Finally the conclusion is drawn that Sequential Gaussian Simulation applied for reserves update can reproduce grade distribution of experimental data perfectly and it can be help for subsequent production.