Under the condition of orthogonal test, rapeseed straw fiber concrete specimen were made to study the influence of water-cement ratio(0.45, 0.50, 0.55, 0.60), straw fiber length(15~20 mm, >20~25 mm, >25~30 mm, >30~35 mm) and straw fiber volume content(0.50%, 1.00%, 1.50%, 2.00%)on the carbonation depth of rape straw fiber concrete. The orthogonal test result shows that the influence of the three variables on the carbonization resistance of rape straw fiber concrete is water-cement ratio, straw fiber length and straw fiber volume content. The optimal level for carbonization resistance of rape straw fiber concrete is the water-cement ratio of 0.45, the straw fiber length of 30-35 mm, and the straw fiber volume content of 1.50%. The electron microscope scanning observation was found that the addition of straw into ordinary concrete could improve the microporous structure of cement slurry，so that the carbonation depth of concrete can be reduced by up to 35.31%，which indicates its carbonization resistance improves. The carbonation depth prediction model of rape straw fiber concrete was built through regression analysis of the least square method, and it was verified that the dispersion coefficient is close to 0.05.