The　Chinese　government　has　announced　ambitious　carbon　reduction　goals　to　address　climate　change,　however,　there　has　been　limited　scientific　attention　to　the　achievement　of　deep　decarbonization　in　regions　with　insufficient　economic　development.　Moreover,　the　complex　impacts　of　climate　change　mitigation　on　energy　system,　environment　and　economic　development　remain　unclear　in　Northwest　China.　Here　we　construct　a　comprehensive　evaluation　model　system　to　evaluate　the　effects　of　different　climate　mitigation　pathways　in　Qinghai,　Ningxia,　Gansu　and　Xinjiang　provinces.　Results　show　that　the　four　provinces　need　to　vigorously　increase　the　share　of　electricity　that　consumed　in　final　energy　to　53.1-60.0%　and　52.9-62.0%　for　2　degrees　C　and　1.5　degrees　C　target,　respectively,　and　reduce　total　energy　demand　to　11.6-44.4　Mtoe　and　8.2-34.1　Mtoe　in　2050.　Meanwhile,　the　CO2　emissions　for　their　energy　systems　will　reach　peak　by　2025　at　lower　values.　Moreover,　the　synergies　of　CO2　reduction　are　most　conducive　to　abating　SO2　pollution　and　also　contributing　to　decreasing　PM2.5　concentrations.　Additionally,　the　GDP　losses　in　2050　fluctuate　from　5.0　to　21.7　billion　USD　in　the　2　degrees　C　scenario　to　11.5-52.7　billion　USD　in　the　1.5　degrees　C　scenario.　Our　study　provides　practical　guidance　on　achieving　carbon　reductions　in　less　developed　regions　of　China　and　lays　foundations　to　promote　decarbonization　of　energy　systems　in　other　provinces.