The infrared radiation transfer should be considered together with other heat transfer process in the phase change of the semitransparent medium. Solidification heat transfer via absorbing, emitting and isotropically scattering in 2-D rectangular semitransparent medium were analyzed. Solidification was assumed to occur over a range of temperatures, and liquid-, mushy- and solid-zones were considered. The enthalpy-based energy equation was solved by the finite volume method. The infrared radiation transfer was solved by the Monte-Carlo method. The results of 1-D phase change heat conduction and 2-D transient coupled infrared radiation and conduction were in good agreements with published data. Effects of various parameters, such as extinction coefficient, refractive index, conduction-radiation parameter and latent heat, et al., on temperature and liquid fraction distributions in the medium were studied. Some of these thermal optical property parameters were found to have significant effects on the results.