This paper presents thermal and optical properties related to the solar thermal energy such as heat storage capacity, thermal conductivity, thermal diffusivity and extinction coefficient of paraffin-based MWCNT nanofluids. For experimental study, paraffin-based MWCNT nanofluids is manufactured by tip sonicator (20 kHz, 200W) with paraffin wax (MP: 58-62℃) as base fluid and MWCNT nanoparticle. With the paraffin-based MWCNT nanolfluids, we measure thermal conductivity, heat capacity and extinction coefficient using transient hot wire method, differential scanning calorimetry (DSC) analysis and laser scattering method respectively. Based on the results, the storage capacity as well as absorption characteristics for solar thermal energy are presented.