Graphitic carbon nitride (g-C3N4) based hybrid photocatalysts have recently emerged as a new class of functional materials for solar energy conversion. Here, we synthesized a novel visible-light-responsive Ag-assisted attapulgite/g-C3N4 composite photocatalyst (ATP/g-C3N4-Ag) by depositing Ag nanoparticles onto the surface of ATP/g-C3N4, which is fabricated by introducing a thin layer of g-C3N4 onto the ATP surface (pre-grafted by (3-glycidyloxypropyl) trimethoxysilane (KH560)). The products were fully characterized by XRD, FT-IR, BET, XPS, UV-vis, TEM and Raman techniques. Results show that g-C3N4 thin layer is uniformly loaded onto the ATP surface by forming a new chemical bond (Si-O-C), which results from the bimolecular nucleophilic substitution reaction (S(N)2) between KH560 and melamine. Comparing with g-C3N4 and ATP/g-C3N4, ATP/g-C3N4-Ag exhibits remarkably enhanced visible light photocatalytic activity in degradation of methyl orange (MO). The highest decomposition rate of MO reaches 96.70% within 20 min, which remains unchanged after 4 cycles. The possible photocatalytic mechanism is investigated by photoluminescence, electrochemical impedance spectroscopy analysis, and radical trapping experiments. Results suggest that center dot OH and center dot O-2(-) are the main active species, and numerous electrons on the Ag surface will be utilized to generate considerable amount of center dot O-2(-) and center dot OH for the degradation of MO.