Herein,　the　alkynyl　groups　are　grafted　on　g-C3N4　via　ball　milling　of　g-C3N4　and　CaC2.　The　successful　functionalization　of　g-C3N4　by　alkynyl　is　demonstrated　by　Fourier　transform　infrared　spectroscopy　and　X-ray　photoelectron　spectroscopy.　Ultrathin　wrinkle-like　structure　with　abundant　pores　is　observed　for　the　resulted　alkynyl　functionalized　g-C3N4　nanosheets,　which　can　furnish　abundant　photocatalytic　active　sites.　The　photocatalytic　NH3　production　rate　of　0.12　mmol·gcat-1·h−1　is　gained　for　alkynyl　functionalized　g-C3N4　under　UV–visible　irradiation,　which　is　2.0-folds　higher　than　pristine　g-C3N4　(0.058　mmol·gcat-1·h−1).　A　maximum　of　1.9　and　1.5　folds　enhancements　are　achieved　for　the　photodegradation　of　rhodamine　B　and　levofloxacin　over　functionalized　g-C3N4　compared　to　pristine　g-C3N4.　The　improved　mechanism　is　investigated　by　linear　sweep　voltammetry,　transient　photo-current,　Tafel　plots,　electrochemical　impedance　spectroscopy,　Mott-Schottky　curves,　turnover　frequency,　transient　decay　time,　photoluminescence　spectra,　etc.　The　modification　technique　proposed　in　this　paper　can　also　be　adopted　to　prepare　other　alkynyl　functionalized　semiconductors　for　photocatalytic　application.　©　2021　Elsevier　B.V.