Thermo-physical properties of diamond reinforced Al composites were investigated. Volume fraction of diamond particles was up to 55%. In order to improve the interfacial bonding between diamond and aluminum, diamond particles were pre-coated with titanium using molten salt method. XRD and SEM observation showed that the Ti coating on diamond consists of carbide layer and metal layer, which mainly depend on temperature and time. The influences of the Ti coating on interfacial characteristic and the thermo-physical properties of the composites were studied. The interfacial characterization and thermal diffusivity measurements indicated that Ti coated diamond was more favorable on interfacial bonding and thermal properties. Ti coating on diamond resulted in an increase of thermal conductivity of the composites, from 200 to 430 W/mK along with a coefficient of thermal expansion of 6.40 × 10-6/K.