A computational code JLULP1 of plasma produced by laser irradiating rectangular target written by us is reported. By using this code, the spatial distrubutional and time-dependent properties of plasma produced by laser irradiating rectangular Sitarget, and the relations of plasma properties with shapes of target have been investigated for the first time. Comparison with the plasma produced by cylindrical target shows that the plasma produced by rectangular target favours three-body recombination.