Aiming at the problem that the backfill grouting of the shield project must have a short setting time and maintain good fluidity, Rapid hardening sulfoaluminate cement (R·SAC) and triethanolamine (TEA) are used as external accelerated setting materials, Analysis of the influence law and microscopic mechanism of the two on grout properties. The results show that with the increase of R·SAC, the setting time of the grout decreases from 9.5 h to 2.0 h, but the fluidity loss at 150 min is about 50%; With 0.6% dosage of TEA as the inflection point, the setting time and fluidity of the grout both increased first and then decreased; In compound blending, The two have a synergistic effect on grout hydration, rapid hydration in the initial stage, shortened setting time, and TEA deflocculation improves grout fluidity and slows down the loss of fluidity over time; By adding 15% R·SAC and 0.05% TEA, a fast-setting and high-fluidity backfill with a setting time of 6 h and a fluidity of 250 mm in 150 min can be prepared.