Compared with Ag2O and Ag3PO4, the advantageous transfer of carriers in Ag6Si2O7 is found responsible for its high photocatalytic activity. The multiple Ag-O units in Ag6Si2O7 result in the separated distribution of holes and electrons. Built-in electric field promotes the transfer of electrons and holes in different regions then reduces the recombination of carriers. The most stable (100) surface of Ag6Si2O7 with holes trapped at surface layers is also beneficial to the photo-oxidation reaction.