Abstract: Variation of shear strength scale-effect of rock mass discontinuity need to be tested on a special integrative direct shear apparatus, where the stable mechanical shear strength parameters can be gotten. A new integrative direct shear apparatus has been developed by two devices. It meets a group of multi-scale rock masses which cross section are from 10x10 to 100x100 cm2. Specimen overlay region and load overlay region are set up to check the accuracy of two devices, where common upper or lower specimens and its corresponding load values can be tested in respective device. The integrative direct shear apparatus has been manufactured and applied. It has been gotten good performances and met the precision and testing requirements. It can be summarized as the following characteristics: (1) It can achieve the transmission, location, directional shearing and restoration of multi-scale specimens, (2) The reliability of the test results and the service life of core components have been verified under precision requirements. Rock mass discontinuity has the peak shear strength and the nearly linear variation for the peak and residual strengths which are consistent with theoretical results and (3) The whole test process is convenient. It has the capability of automatic collection and real-time graphics by self-developed software. The integrative direct shear apparatus has provided a good platform to research shear strength of multi-scale rock masses.