This paper designs the resistor that can convert the range automatically and preset the resist-ance． The circuit of the resistor consists of the range conversion circuit，the gain setting circuit，and the con-trol circuit． There is no register in resistor circuit，and the resistor has many advantages of multiple ranges，thecontinuous resistance adjusting，high resolution and accuracy． To improve the resistor resolution and the rangeconversion speed and eliminate the resistance error and lead wire error，the paper designs the detailed circuitto test the resolution and accuracy of the system． By analyzing the measured data，when the resistance valuerange is 0 ～ 1 kΩ，the resolution can reach 0 ． 1 Ω，and when the resistance value range is more than 1 kΩ，the resolution can reach 1 Ω．