Abstract: The fine and medium grain gabbros from Jianshan mining area of Panzhihua city were tested through the rock mechanical tests, such as suniaxial compression test, conventional triaxial compression test, tensile strength test and softening test. And the influence of rock structure (mineral grains), water and the confining pressure on properties of strength and deformation of rocks were analyzed. The experimental results indicated that uniaxial compressive strength, elastic modulus and ratio of compression to tension of the fine grain gabbro are superior to those of medium grain gabbro. But the experimental results from triaxial compression test showed that no much difference in peak strength, residual strength and elastic modulus were observed between fine and medium grain gabbros. And Cof fine grained gabbro is higher than that of medium grain gabbro but with lower φ. Peak strength and residual strength have an approximate linear relation with the confining pressure when confining pressure increased. And the slight increase in elastic modulus E, significant increase in deformation modulus E50, decrease in shear failure angle and higher softening coefficient were also observed. Under the saturation condition elastic modulus reduced and Poisson's ratio increased.