[Objective] The effects of different preparation temperatures for hydrochars from sunflower straw on soil organic carbon （SOC） and its components were investigated to provide a theoretical basis for sunflower straw resource utilization and soil carbon sequestration. [Methods] Hydrochars （SB180 and SB220） were prepared from sunflower straw at 180 ℃ and 220 ℃， respectively， and indoor incubation tests were conducted to analyze the differential regulation of SOC and its fractions by varying preparation temperatures and additive amounts of hydrochar input. [Results] ① The carbon content， aromaticity， specific surface area， and pore volume of the hydrochars gradually increased with increasing preparation temperature. ② The contents of SOC， mineral-associated organic carbon （MAOC）， and particulate organic carbon （POC） significantly increased with increasing preparation temperature and addition amount. SOC， POC and MAOC reached their highest levels in the 2% SB220 treatment， increasing by 75.34%， 23.34% and 105.75%， respectively， compared with CK. ③ As the preparation temperature increased， the soil organic carbon mineralization rate， cumulative mineralization amount， potentially mineralizable carbon （C_p） and priming effect （P_E） decreased， whereas these values increased with higher addition amounts cumulative mineralization， C_p and P_E were elevated by 50.88%， 57.61% and 79.51%， respectively， in 2%SB220 treatment compared to 1%SB220 . [Conclusion] SB220 can significantly enhance the contents of SOC， MAOC and POC， and exhibits strong carbon sequestration potential； however， the risk of carbon emissions increases with the increase of the addition amount. Therefore， it is recommended to add 1%SB220 to achieve a balance between mineralization loss and long-lasting sequestration.