<p>A ternary early-strengthening agent consisting of calcium formate + triethanolamine + lithium sulfate was compounded with quercetin to shorten the setting time of cementitious materials while ensuring their early strength. The optimum ratio of the three early-strengthening agents was determined as 0.5% calcium formate + 0.04% triethanolamine + 0.4% lithium sulfate by response surface methodology. The effects of the ternary early-strengthening agent composed of calcium formate + triethanolamine(TEA)+ lithium sulfate on cementitious pore sealing materials under the synergistic effect of quercetin were studied by means of the performance tests of compressive strength, fluidity, and setting time, and the microstructural characterizations of X-ray powder diffractometer(XRD), thermogravimetry (TG-DSC) and scanning electron microscopy (SEM). The study shows that the synergistic effect of ternary early-strengthening agent and quercetin forms a multiperformance composite admixture for cementitious materials. The best performance was obtained with the compounding scheme of 0.5% calcium formate + 0.04% triethanolamine + 0.4% lithium sulfate ternary early-strengthening agent and 0.05% quercetin. The compressive strength of 1, 3, 7, and 28 d are 94.8%, 39.8%, 42%, and 28% higher than those of the blank group, respectively. The initial time and final setting time are 41 and 57 minutes, respectively. According to the microscopic analysis, the network and fibrous C-S-H gels generated by ternary early-strengthening agents are attached to the surface promoted by quercetin, which forms skeleton support while thickening and solidifying the cement slurry, which enhances the early compressive strength of the cement-based materials.</p>