The current transducer is the important measurement in power system, it plays more and more significant role in power system analysis, relay protection and current measurement. With the improvement of transmission capacity of power system, traditional electromagnetic current transducer exposed more and more defects, and it is difficult for traditional electromagnetic current transducer to meet requirement of power automatic and digital development. Recent years, with the development of optoelectronic technology, fiber current transducer emerged and received extensive attention of researchers at home and abroad, and the research of fiber current transducer has been significant research area. More important, display instrument of fiber current transducer is the difficulty to solve. The special display instrument was proposed in this paper. First, the effective value chip was utilized to sample alternating signal and output effective value. Second, single chip computer and signal process technology were utilized in this instrument, single chip computer be in charge of algorithm computing and data display processing. By numeral simulation and experiment, the error of designed special display instrument was 0.04%. So this instrument can meet the requirement of 0.2 level National Standard, it is suitable for fiber current transducer to measure small current.