Rolling-diffusion　bonding　experiments　were　performed　on　steel/Cu/steel　system　using　50　μm　thick　copper　as　inter-layer.　The　effect　of　plastic　deformation　on　bonding　strength　and　interlayer　thickness　was　investigated.　Based　on　experiments,　the　kinetics　of　isothermal　solidification　was　systematically　studied.　And　a　numerical　model　of　isothermal　solidification　time　was　developed.　The　results　show　that　the　isothermal　solidification　time　is　obviously　reduced　due　to　the　effect　of　plastic　deformation.　A　reasonable　isothermal　solidification　time　was　obtained　when　an　effective　diffusion　coefficient　was　used,　indicating　the　intercrystalline　and　grain　boundary　diffusion　of　Cu　in　steel　play　an　important　role.　The　evolution　of　interlayer　thickness　indicates　a　good　agreement　between　the　calculation　results　and　experimental　measurement.