Co-gasification of biomass after hydrothermal treatment (HTT) and coal blends had great potential to realize the clean and efficient co-conversion of biomass and coal. In this study, co-gasification reactivity and synergy of Shenfu bituminous coal and rice straw (RS) hydrochar (prepared at HTT temperatures of 200, 220, and 240 degrees C) blends (denoted as SF-RS200, SF-RS220, and SF-RS240) were investigated using a nonisothermal thermogravimetric analysis, and gasification kinetic analysis was conducted based on the Coats-Redfern method. The results show that different blends showed little difference in the initial temperature for weight loss, the final temperature for weight loss, and the temperature corresponding to the maximum weight loss rate during both co-pyrolysis (stage 1) and blended char co-gasification (stage 2), and only the maximum weight loss rate of different blends showed a relatively large difference. Reactivity of blends at both stage 1 and stage 2 decreased at a higher HTT temperature. There was no synergy behavior at stage 1. However, the synergistic effect at stage 2 was observed and was more significant for SF-RS200 and SF-RS220 compared with SF-RS240, which was mainly attributed to the potassium concentration difference among RS hydrochar samples led to various catalytic effects on coal char gasification at stage 2. Kinetics analysis demonstrates that both volumetric reaction model (O1) and shrinking core model (R2, R3) all showed high correlation coefficients (>0.95) for different samples and reaction stages. There were obvious kinetic compensation effects in the gasification process, and activation energy (E) and pre-exponential factor (A) of different samples followed a positive correlation relationship as In A = 0.2340 x E - 4.3186 for stage 1 and In A = 0.1217 x E - 6.2181 for stage 2.