Transition　metal　oxide-mediated　heterogeneous　peroxymonosulfate　(PMS)　activation　on　organic　pollutant　degradation　has　attracted　much　attention,　where　continuous　redox　cycling　between　high　and　low　valence　metal　ions　is　the　key　step　as　it　relates　to　the　radical　generation.　Herein,　a　composite　PMS　activator　of　S-doped　g-C3N4/　NiCo2O4　(CNS_NCO)　was　constructed　and　exhibited　excellent　tetracycline　(TC)　degradation　performance　with　96.9%　removal　efficiency　within　30　min.　Experimental　and　theoretical　calculations　indicated　that　S　doping　not　only　widened　the　difference　in　the　work　function　of　CNS　and　NCO,　but　also　enhanced　the　built-in　electric　field　intensity　of　CNS_NCO　heterojunctions,　resulting　in　more　electron　transfer　from　CNS　to　NCO　in　a　directional　manner　and　accelerating　the　Co(III)/Co(II)　and　Ni(III)/Ni(II)　redox　cycle　to　form　more　reactive　oxygen　species　(ROS).　It　was　demonstrated　that　1O2　(main　ROS)　was　formed　mainly　through　SO4　&　BULL;,　&　BULL;OH　and　&　BULL;O2　　(minor　ROS)　conversion.　Meanwhile,　high-valent　cobalt-oxo　(CoIV　=　O)　species　also　played　an　important　role　in　TC　degradation.