The addition of accelerators to concrete can shorten the setting time of concrete and has become an indispensable admixture in shotcrete. The alkali-free and fluorine-free liquid accelerator, which features stable strength development and good environmental performance, has gradually become one of the research hotspots in the field of shotcrete. In this paper, a mother liquid of alkali-free and fluorine-free liquid accelerator was prepared using polymeric aluminium sulfate, diethanolamine, magnesium sulfate and ethylene glycol as the main raw materials. The proportion was further optimized by adding enhancing and stabilizing components, and an appropriate proportion of high-early-strength alkali-free and fluorine-free liquid accelerator was determined: polymeric aluminium sulfate: diethanolamine: ethylene glycol: magnesium sulfate heptahydrate: nano-silica: QM stabilizer: dilute sulfuric acid: water = 57:6:1:2:2:3:1:28. When the dosage of the new liquid accelerator was 7% of the cement mass, the initial setting time and final setting time of the cement paste were 2 min 30 s and 7 min 25 s, respectively. The compressive strengths of the cement mortar at 6 h, 1 d and 28 d were 1.5 MPa, 12.4 MPa and 52.2 MPa, respectively, and the compressive strength retention rate at 90 d was 117.03%. The effects of the high-early-strength alkali-free and fluorine-free liquid accelerator on the cement hydration process and hydration products were studied through micro tests such as heat of hydration, thermogravimetric analysis and XRD.