A huge increase in performance of devices within the sizes and weight decrease result in high performance thermal interface materials (TIM) are indispensable to application. Thermal grease is one of the most commonly used TIM types. Zinc-oxide based thermal grease (KPT-8) has a low thermal conductivity that leads to overheating. New silicone oil – aluminum nitride high performance thermal grease has been studied. Also the installation for thermal conductivity investigation has been designed and produced. Thermal conductivity value of aluminum nitride-silicone oil thermal grease with 50 % volume fraction was 1,130±0,056 W/(m K), that is 40 % higher than KPT-8 thermal conductivity. Thermal conductivity value was calculated by a number of theoretical models, and the results were compared to the experimental data. The best results have been obtained by modeling within Brugemman and Cheng-Vachon theories.