Aiming at the urgent cooling demand of 5G base stations，a kind of Ｒoll bond Aluminum Vapor Chamber (RAVC) ，made from hollow aluminum substrate formed by printing，rolling，inflating，degassing，injecting and sealing processes，was prepared． The thermal performance of RAVC，such as thermal resistance and capacity，un- der different filling ratios and working conditions was investigated． The results indicate that RAVC shows best ther- mal performance under gravity working condition． The thermal conductivity can reach 19900 W/( m·K) when filling ratio is 10% and heating power is 60 W; RAVC reaches the heat transfer limit when filling ratio is 5% and heating power is over 60W; temperature oscillation occurs when filling ratio is over 25% and heating power is under 10W． Under horizontal and anti-gravity working conditions，RAVC's thermal performance becomes worse，and its start-up performance in horizontal state is better than that under anti-gravity working condition，but its thermal performance is not better until it becomes stable．