Abstract: In order to study the influence of coarse aggregate size on the mechanical properties of concrete,the quasi-static compression and splitting tensile experiments of M40,M80 and M110 mortars and concrete with different coarse aggregate sizes were conducted by MTS. The quasi-static compressive stress-strain curve and splitting stress-time curve of each specimen were obtained. Then,the influence of coarse aggregate size on different grade concrete was analyzed. Moreover,the influence of mortar compressive strength and aggregate size on concrete compressive strength was studied by means of two-way analysis of variance. The results show that the compressive strength,Young's modulus and tensile strength of concrete have a similar change tendency with the coarse aggregate size increased,in other words,the tendency of first increasing and then decreasing. The effect of coarse aggregate size on the concrete compressive strength is increased with mortar strength increasing,but the influence on Young's modules is decreased with the mortar strength increased. The influence of mortar compressive strength on concrete compressive strength is greater than that of aggregate size.