Grid-forming　inverters,　which　are　represented　by　droop　control　and　virtual　synchronous　generator　control,　have　been　widely　studied　and　applied　because　of　their　excellent　grid-supporting　ability　and　smooth　off-grid　switching.　When　a　grid-forming　inverter　is　connected　to　a　microgrid　or　utility　grid,　the　control　loops　of　active　power　and　reactive　power　will　be　coupled　because　of　the　voltage　phase　difference,　which　will　affect　the　power　control　performance.　This　paper　first　derives　the　small-signal　linearized　model　of　the　system,　based　on　which　a　frequency　feedforward　control　and　an　amplitude　feedforward　control　are　proposed　to　decouple　the　active　power　and　reactive　power　control　loops,　respectively.　The　proposed　decoupling　strategy　directly　modifies　the　reference　values　through　feedforward　with　an　easily　implementable　principle　that　is　applicable　to　various　control　coordinate　systems,　control　coordinate　systems,　and　control　structures.　By　comparing　system　models　with　and　without　the　proposed　decoupling　strategy,　its　effectiveness　can　be　theoretically　proven.　Time-domain　simulations　and　hardware　experiments　are　presented　to　further　validate　its　effectiveness.