The influence of complexing agents including formic acid, oxalic acid and phosphoric acid on the storage stability of aluminum sulfate-based alkali-free liquid accelerator (LA), the setting time of cement paste and the compressive strength of mortar were studied in the present research. And their mechanism were investigated by analyzing hydration process as well as the phase composition and microscopic morphology of cement paste containing aluminum sulfate-based LA using hydration heat flow calorimetry, X-ray diffraction (XRD), thermogravimetric-derivative thermogravimetric (TG-DTG) analysis and scanning electron microscope (SEM). The results show that three kinds of complexing agents improved the storage stability of aluminum sulfate-based LA, and their effect was in the order of phosphoric acid > formic acid > oxalic acid. At the same aluminum sulfate proportion, with the introduction of three individual complexing agent into aluminum sulfate-based LA, the setting time of cement paste was shortened significantly. Among three complexing agents, their effect on improving the accelerating effect of aluminum sulfate-based LA was in the order of formic acid > oxalic acid > phosphoric acid. Using oxalic acid as complexing agent improved the early strength effect of aluminum sulfate-based LA, while phosphoric acid was beneficial to improving the 28 d compressive strength of mortar. The acid radical ions of complexing agents can form a stable complex with Al³⁺ in aluminum sulfate-based LA, which can increase the content of Al³⁺ and the amount of AFt formed in the hydrated system, thus enhance the accelerating and early strength effect of aluminum sulfate-based LA.