Using red mud， fly ash， desulfurized gypsum and an alkaline solid waste admixture as cementitious materials and coal gangue as aggregate， an environmentally friendly all industrial solid waste pavement base mixture （RFDC） was prepared. The development laws of unconfined compressive strength（f_UCS） and splitting tensile strength（f_STS） of RFDC with different fly ash contents at 4 ages （7， 28， 56 and 90 d） were studied. Then the failure modes of the compressive and splitting tensile specimens were analyzed. The correlation between the molar ratio of three different oxides in solid waste cementitious materials and 7 d f_UCS of the RFDC was discussed. The formation mechanism of RFDC strength was revealed. The results show that when the content of fly ash is 15%， the mechanical properties of the RFDC are the best. The compressive specimen presents a typical central compressive failure， and the split tensile specimen is damaged by coarse aggregate of coal gangue. The n（CaO）/［n（SiO₂）+n（Al₂O₃）］ value of the solid waste cementitious material has the closest correlation with the 7 d f_UCS of the RFDC. Ettringite（AFt），aluminum-modified calcium silicate hydrate（C-（A）-S-H） gel and zeolite-like substances are the main hydration products that provide strength to the RFDC.