Thermal interface material (TIM) technology is of great importance in the 3D system packaging. In this paper, the preparation of thermal interface materials using vertically aligned carbon nanotube (VACNT) array and its characterization were investigated. The transfer process of VACNT was successfully performed by a Ti/Ni/Au metal layer with a thickness of 50/100/100 nm and Sn64Bi35Ag1 solder. A thermal release adhesive tape (Nitto Denko, Part Number: #3198MS) was used to obtain suspended VACNT array. The LFA 447 was used to characterize the thermal diffusivity α(T) and apparent thermal conductivity λ(T) of VACNT array at 25℃, 75℃ and 125℃, respectively. Thermal cycle reliability test was also carried out. Results show that the apparent λ(T) is over 42 W/(m·K) for VACNT array on the Si growth substrate and over 41 W/(m·K) for transferred CNT array. After 200 thermal cycles, the λ(T) is over 28 W/(m·K) for CNT array on its Si growth substrate and over 24 W/(m·K) for transferred CNT array.