Based on its high ash activity and filling effect, silica fume was added in ordinary concrete which was formerly added with rape straw ash to solve the problem of low early strength of the rape straw concrete, and the work and the mechanical performance of the double mixed concrete were investigated. The results showed when rape straw ash content was 20%, the cohesive properties and the water retention properties become better with increasing content of silica fume; when the silica fume content was 10%, the compressive strength of the concrete reached 17.2 MPa, which was increased by 24%; when the rape straw ash content was 20% and the silica fume content was 6%, the optimum range of water-cementitious material ratio of the double mixed concrete was 0.5–0.6.