In this paper, Ag-based g-C3N4 composites have been successfully fabricated through two deferent synthetic methods: (i) a facile and efficient precipitation-calcination strategy (denoted as D-CN-xAg, x represents the dosage of Ag2CO3, the same below), (ii) a calcination method (denoted as Z-CN-xAg). All Ag-based g-C3N4 composites exhibit the enhanced photocatalytic activities under visible-light irradiation. Moreover, the optimal dosage of Ag2CO3 in the D-CN-xAg composite is found to be 5%, the corresponding hydrogen production capacity is 153.33 mu mol g(-1) h(-1), which is 4.6 times higher than that of Z-CN-5%Ag composite. This might be attributed to appropriate content of metallic Ag and more active sites exposed on the surface of D-CN-5%Ag composite. Meanwhile, combining with photoelectrochemical results, it could be inferred that LSPR effect and the intimate interfacial between metallic Ag and g-C3N4 in the system play also important role for the improvement of photocatalytic activity. These results demonstrate that the appropriate loading of metallic Ag originated from Ag2CO3 into g-C3N4 could accelerate the separation and transfer of photogenerated electron-hole pairs, leading to the improvement of photocatalytic activity for hydrogen production from water splitting. Finally, a possible photocatalytic mechanism is proposed. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.