Three different loading methods, i.e. arc-holder, direct-holder and middle-steel-wire-holder, are used to determine the tensile strength of sandstone, mudstone. The results show that there is a great difference of tensile strength for the same rock by using different loading methods, the measured tensile strength for arc-holder loading method is maximum, one is middle for direct-holder loading method and one for middle-steel-wire-holder is least. The stress field and the failure patterns of the rock specimens are analyzed base on MATLAB and FLAC2D. The results show that for hard rock the initial failure is not sure at the center of specimen, but may is at the some place along the axial line of specimen; for soft rock and layered rock the failure patterns are different rocks when different loading methods are used. The differences of the tensile strengths measured using different loading methods are caused by the friction existing between the holder and the specimen and so on. This paper gives the calculation equation of rock's tensile strength for different loading methods.