Plastic　deformation　was　newly　introduced　in　transient　liquid　phase　(TLP)　diffusion　bonding　of　steel　sandwich　panels.　The　effect　of　plastic　deformation　on　bonding　strength　was　investigated　through　lab　experiments.　It　was　assumed　that　three　factors,　including　newly　generated　metal　surface　area,　deformation　heat,　and　lattice　distortion,　contribute　to　the　acceleration　of　interface　atoms　diffusion　and　increase　of　diffusion　coefficients.　A　numerical　model　of　isothermal　solidification　time　was　developed　for　TLP　bonding　process　under　plastic　deformation　and　applied　to　carbon　steel　sandwich　panels　bonding　with　copper　interlayer.　A　reasonable　isothermal　solidification　time　was　obtained　when　an　effective　diffusion　coefficient　was　used.　Based　on　lab　experiments,　the　effects　of　plastic　deformation　on　interlayer　film　thickness　and　isothermal　solidification　time　were　studied　through　theoretical　calculation　with　the　new　model.　The　evolution　of　interlayer　film　thickness　indicates　a　good　agreement　between　the　calculation　and　experimental　measurement.　The　results　show　that　the　isothermal　solidification　time　is　obviously　reduced　due　to　the　effect　of　plastic　deformation.　Furthermore,　a　new　steel　sandwich　cooling　panel　for　heat　exchanger　was　fabricated　by　TLP　diffusion　bonding　under　13.1%　plastic　deformation.　The　test　results　suggest　that　a　steel　sandwich　panel　of　inequidistant　fin　structure　can　provide　enhanced　heat　transfer　efficiency.