The invention provides an encryption and decryption functions based field service terminal, which comprises a control processing unit, a main-station communication unit, an equipment communication unit, a power supply unit, an input and output unit, a safety unit and a smart card reading and writing unit. The control processing unit is respectively connected with the control processing unit, the main-station communication unit, the equipment communication unit, the power supply unit, the input and output unit, the safety unit and the smart card reading and writing unit. The safety unit is used for completing identity authentication and encryption and decryption of data information when the field service terminal is in communication with a main station and power energy meters, and the smart card reading and writing unit is used for field card writing and recharging of local charge-control smart power energy meters. The encryption and decryption function based field service terminal has the advantages that field service efficiency and quality are improved; the safety unit is added, so that transmission data of the field service terminal cannot be distorted, data confidentiality and integrity cannot be damaged and identities of users cannot be used falsely; and the requirement of power-utilization information acquiring system construction for power consumers can be met basically.