Abstract: A new in-situ direct shear testing method for large-grained rockfill materials is introduced. The distinctive feature of this new in-situ direct shear testing method is to pull the shearing frame with a flexible chain, which causes the mutual movement of the shearing frame and the specimen during shear. Thus, the wall friction of the shearing frame has little influence upon the normal stress on the shear plane and the correct measurement for the shear strength becomes possible in the new direct shear test. There are many applications of this new testing method abroad, however, it is the first time in China to use this method in the upper reservoir of Yixing Pumped Storage Power Station Project.