The invention discloses a block chain service device which comprises a processor, a networking circuit, a power supply circuit, a memory and a hardware dismounting prevention circuit. The invention further discloses a block chain service system, which comprises a plurality of network terminals and a plurality of block chain service devices, wherein at least one block chain service device acts as a block chain service device server, and at least one block chain service device acts as a block chain service device client. The invention also provides a communication method of the block chain service system. According to the invention, block chain data of the block chain service device is stored in the block chain service device, access can only be available through authorization, no delete interface is provided, the power consumption is small, and the block chain service device can operate for 24 hours. The block chain service system and the communication method thereof realize point-to-point block chain services by relying on the block chain service device and need not rely on a computer to act as an intermediary. The block chain service device, the block chain service system and the communication method thereof can be widely applied to the field of block chains.