A　new　method　of　calculating　the　angle　parameter　in　FRFT　domain　based　on　the　eigenfunction　of　time-varying　channel　is　proposed　in　this　letter　for　FRFT-OFDM　systems.　The　new　scheme　can　estimate　the　angle　parameter　in　real　time　based　on　the　variation　of　the　wireless　channel.　The　relationship　between　the　time-variant　frequency　of　G-eigenfunction　and　time　is　approximated　by　linear　function.　Both　theoretical　analysis　and　computer　simulation　demonstrate　that　the　new　scheme　has　a　low　complexity　compared　with　the　traditional　method.　When　the　number　of　subcarriers　is　128,　the　new　scheme　can　reduce　the　complexity　by　104compared　with　the　traditional　method.　This　new　scheme　has　advantage　when　the　Doppler　spread　is　large　or　the　time　variation　of　the　channel　is　fast.