With the development of global information industry, the scale of data centers become larger, meanwhile the energy consumption and running cost are grown rapidly. The energy saving problem of data center has been more and more concerned around the world. The energy consumption of data centers in Beijing was studied in this paper. The results show that the energy utilization problem of cooling systems is especially prominent, and their average energy consumptions account for 47% in these data centers. With the proposal of energy saving in cooling system, heat pipe cooling system is introduced in this paper. As free cooling utilization device, when the outdoor temperature is lower than the environment set temperature, the data center can be cooled by the outdoor cold environment through this system, and the energy consumption of cooling system will be reduced significantly. At present, this system has been applied in dozens of data centers and communication base stations in China and the energy saving effects are obvious. Case studies show that after using the heat pipe cooling systems, the cooling systems of data center and the communication base station can separately achieve the energy saving of 38.9% and 55.7%.