The data transmission distance of passive inductive data transmission system is short due to the great metal eddy current loss and the small size of receiver antenna in application environment. To overcome the problems, a class C power amplifier was designed and the circle transmitting antenna was improved in the transmitter，while a steady electric charge pump circuit and a low power consuming processor PIC16LF877A were adopted in the receiver. The transmission distance has been increased via these methods. The transmission distance of the designed system is 15 cm，which can transmit data reliably in real time with steady performance.