By the test study of basic mechanics properties of concrete with different fly ash content, the influence of the content of fly ash on the compressive strength, flexural strength, splitting tensile strength and static compressive elastic modulus of concrete are analyzed with the explaining of the influence mechanism of fly ash. The test results show that, comparing with the normal reference concrete, the early age strength of fly ash concrete enhances slowly, while the late strength develops rapidly, even overpasses the strength of normal reference concrete.