Abundant　spin-related　phenomena　that　originate　from　interfaces　between　ferromagnetic　electrodes　and　molecular　semiconductors　have　greatly　enriched　research　in　spintronics,　and　they　are　considered　promising　for　realizing　novel　spintronic　functionalities　in　the　future.　However,　despite　great　effort,　the　interfacial　effect　cannot　be　precisely　controlled　to　achieve　steady　and　predictable　functions,　especially　at　room　temperature,　and　this　has　gradually　become　a　significant　bottleneck　in　the　development　of　molecular　spintronics.　In　this　study,　an　innovative　spin-filtering-competition　mechanism　is　proposed　to　continuously　modulate　the　interfacial　effect　in　molecular　spin　valves　at　room　temperature.　To　form　this　novel　mechanism,　the　original　spin-filtering　effect　from　pure　cobalt　competes　with　the　newly　generated　one,　which　is　induced　by　the　bonding　effect　between　cobalt　and　lithium　fluoride.　Subsequently,　by　precisely　controlling　competition　through　lithium　fluoride　coverage　on　the　cobalt　surface,　continuous　modulation　of　the　spin-injection　process　can　be　successfully　achieved　at　room　temperature.　Spin　polarization　of　the　injected　current　and　magnetoresistance　effect　can　be　actively　controlled　or　their　sign　can　be　completely　reversed　through　this　novel　mechanism.　This　study　provides　an　innovative　approach　and　theory　for　precisely　controlling　spin-related　interfacial　effects,　which　may　further　promote　the　scientific　and　technological　development　of　spintronics.