Peanut straw and canola straw biochars produced with self-made biomass carbonization furnace and rice hell biochar collected from a gas gasification station were used to investigate amelioration effects of crop residue-derived biochars on soil acidity and canola yield in red soil. Results indicated that the application of all the three materials effectively increased soil pH and decreased soil exchangeable acidity. The amelioration effects of the biochars were primarily dependent on their alkalinity. Application of peanut straw and canola straw biochars significantly increased soil exchangeable base cations, available phosphorus, effective cation exchange capacity and base saturation, and thus increased the canola yield under field conditions. Soil pH for the treatments with peanut straw and canola straw biochars applied still higher than that for the control after 3 years of the soil amended with the biochars, suggesting that the ameliorating effect of the biochars on red soil is lasting. The amelioration effect on soil acidity and fertility in the red soil intensified with the application rates. Thus, peanut straw and canola straw biochars are good amendments for acid red soils.