Abstract: Objective The reservoir sediment is large in quantity, and is in fluid and plastic states, and the bearing capacity is poor, and the treatment is difficult, so it is urgent to find the reservoir sediment treatment method. Method The influence of thermal activation and chemical activation of reservoir sediment on the properties of reservoir sediment-cement composite cementitious material was studied by experiments of fluidity, setting time and mechanical strength. Result The results showed that the strength of the mortar specimen was improved after thermal activation, but the setting time was greater than 6.5 h, and the fluidity decreased. When the thermal activation temperature was 700 ℃, the 28 d flexural strength and compressive strength of the mortar specimen were 6.71 and 36.88 MPa, respectively, and the fluidity of the mortar specimen was only 109 mm. At the coupled activation of thermal and chemical activation, the setting time was less than 6.5 h, and the fluidity increased. When the addition of Na₂SiO₃ was 3%, the fluidity of the mortar increased by 13.8%, and the 28 d flexure and compressive strengths of the mortar specimens were 6.98 and 44.67 MPa, respectively. Conclusion The microcosmic results showed that thermal activation and chemical activation can promote the reservoir sediment to produce more amorphous SiO₂ to participate in the hydration reaction and generate more hydration products. This study can solve the difficult problem of reservoir sediment treatment and provide a new idea for the resource utilization of reservoir sediment.