Bio　oil　was　proved　an　effective　modifier　to　improve　the　compatibility　of　rubber　asphalt.　However,　the　pathway　in　which　the　bio　oil　enhances　the　compatibility　of　rubber　asphalt　remains　unclear.　To　understand　the　role　of　the　bio　oil　in　rubber　asphalt　during　preparation　process,　the　waste　cooking　oil　residue　(WCOR)　was　incorporated　during　the　preparation　of　rubber　asphalt　in　different　scenarios.　The　compatibility　of　the　prepared　rubber　asphalts　was　examined　through　the　cigar　tube　test,　the　rheological　characterization　and　the　morphology　observation.　The　compositional　change　of　ground　tire　rubber　(GTR)　extracted　from　the　prepared　rubber　asphalts　was　analyzed　via　the　thermogravimetric　analysis　(TGA),　and　the　chemical　and　fractional　composition　of　the　asphalt　phase　separated　from　the　three　rubber　asphalts　was　analyzed　via　the　Fourier　transform　infrared　spectroscopy　(FTIR)　test　and　the　thin-layer　chromatography　with　flame　ionization　detection　(TLC-FID)　test.　Results　showed　that　the　compatibility　of　the　rubber　asphalt　with　GTR　swelled　by　WCOR　prior　to　preparation　was　significantly　improved　compared　with　that　of　the　rubber　asphalt　with　untreated　GTR　and　the　rubber　asphalt　prepared　by　blending　GTR　and　WCOR　simultaneously.　The　results　from　chemical　and　compositional　characterization　suggested　that　the　improved　compatibility　of　the　rubber　asphalt　incorporating　GTR　pre-swelled　with　WCOR　was　mainly　attributed　to　the　extended　release　of　nature　rubber　(NR)　and　traces　of　synthetic　rubber　(SR)　and　inorganic　filler　into　the　asphalt　phase.　©　2020　Elsevier　B.V.