To obtain fine-grained products of ultra-deep drawing hot rolled steel sheets,effect of deformation,deformation temperature,deformation rate on microstructure refinement were investigated through multi-pass hot-rolling finish-rolling process test.Experimental results show that gain size decreased with the increase of total deformation and the first-pass deformation in a certain finish rolling temperature range.Gain size decreased with the decrease of deformation temperature and the increase of deformation rate.Through the industrial test rolling,grain size of hot rolled steel sheets was up to 8.5.