Shock and release experiments are performed on the porous Sn with sub-micropores with porosity m=1.01. Time-resolved interfacial velocities between the porous Sn and LiF window are measured with Doppler pins system under seven pressure points from 31.8 GPa to 66.1 GPa. From the interfacial velocity, the Euler longitudinal sound velocities and the bulk sound velocities are obtained. The corresponding Poisson ratio and shear modulus are determined, too. From the transition of longitudinal sound velocity to bulk sound velocity at high pressures, the shock-induced melting of Sn with porosity 1.01 occurs at about 49.1 GPa. With the Euler longitudinal sound velocities, the bulk sound velocities and the shear moduluses of porous and dense Sn, the melting pressure zone of dense Sn can be determined to be between 53.5 GPa and 62.3 GPa. Comparing the melting zone of porous Sn and that of dense Sn, micropores in the material reduce the the shock melting pressure obviously. The Exact shock melting pressure of dense Sn needs further experimental data in the corresponding pressure zone. From the longitudinal velocity of porous Sn in the measured solid zone, no bcc phase transition takes place for this material. This may relate with the micropores in the material or the difference in material component, which needs further investigating.