Abstract: The improvement effect of sodium gluconate on the fluidity and mechanical properties of autoclaved lightweight concrete (ALC) waste-cement system was studied, and the hydration products and microstructure of the hardened cement paste were characterized by XRD, TG-DSC, MIP and SEM. The results show that appropriate content of sodium gluconate can significantly improve the fluidity of the system. When the content of ALC waste is 5%, the fluidity of the system is 230cm by adding 0.04% sodium gluconate, which can meet the performance index of pure cement, and its 28d compressive strength can reach to 59.9MPa, which is higher than that of the samples without sodium gluconate. Meanwhile, the results of XRD, TG-DSC and SEM indicate that much more Ca(OH)2 and C-S-H gel, smaller gap and higher compactness appear in the hydration products of the samples with sodium gluconate. The MIP result shows that sodium gluconate is favorable to reduce the porosity and improve the pore structure of ALC waste-cement system.