To explore the best way of returning straw materials to acidic red soil double-cropping rice fields, this study set up four different straw material treatments: no straw return (CK), direct straw return (SDR), straw extract return (SER), straw organic fertilizer return (SOR), and straw biochar return (SCR). The effects of these treatments on rice yield, soil acidification characteristics, soil cation exchange capacity, and soil fertility were investigated. The results showed that compared with CK, all straw treatments significantly increased the yields of early and late rice, with SCR and SOR having the largest increases (early rice +14.52%, +11.43%, late rice +13.23%, +10.51%, annual +13.81%, +10.92%), while SDR and SER had smaller increases and no significant differences between them. Regarding soil acidification, the pH of all treatments was slightly lower than that of CK, and the exchangeable aluminum, hydrogen, and exchangeable acidity all slightly increased, but the differences were not significant, with SOR having the smallest increase. There were no significant differences in soil cation exchange capacity and total nitrogen, phosphorus, and potassium nutrients compared with CK. Organic carbon, water-soluble nitrogen, and available phosphorus all showed an upward trend, with available phosphorus significantly increasing. SER significantly increased available potassium. It can be seen that returning straw can stabilize and increase yields and improve the supply of available nutrients. Straw biochar return and straw organic fertilizer return had the best comprehensive effects.