The paper describes the operation principle of optically powered sensor to measure differential pressure. Its probe powered by LD light only consumes tens micro watt .The optical source for power and signal can be transmitted to and fro by a single multiple mode optical fiber. The power and signal lights have different wave length. The system design is introduced and its parameters are selected. The signal and power are transmitted by fiber, and the probe is low power consumption, so this pressure measuring system can work in flammable and explosive environment. Adopted differential measuring signal processing technology, its anti-noise ability is improved. Experimental results show that this system has high precision and high reliability.