In　semiconductor-mediated　photocatalysis,　the　optical　property　of　semiconductors　is　a　key　parameter　and　closely　related　to　the　conversion　efficiency　of　solar　energy.　However,　endeavors　in　achieving　a　wide　spectral　response　of　semiconductors　are　still　limited　in　impurity　incorporation　or　using　other　assistants.　Here,　we　report　on　a　structure-distortion-induced　extension　in　the　optical　absorption　of　conjugated　polymer　semiconductors　without　relying　on　any　extra　species,　by　taking　a　typical　example　of　two-dimensional　graphitic　carbon　nitride　(g-C3N4)　nanosheets.　Experimental　and　theoretical　calculation　results　both　identified　the　close　relationship　between　the　band　structure　and　the　structural　distortion　and　the　amount　of　the　layers,　while　keeping　in-plane　fundamental　units　intact　and　the　connecting　mode　invariable　during　the　peeling　process.　Photocatalytic　activity　was　evaluated　toward　hydrogen　evolution　over　different　samples　with　visible　light.　The　results　showed　that　distorted　g-C3N4　exhibited　higher　activity　and　its　wavelength-dependence　activity　can　be　extended　to　550　nm　with　desirable　H-2　production.　This　finding　offers　a　new　channel　for　researchers　to　design　a　polymer　with　photocatalytic　activity　under　its　extending　visible　spectrum.