Abstract: A simple structure frequency extension and low temperature drift oscillator is presented. By temperature compensation and trimming circuit a low temperature current is used to charge and discharge a capacity.Compared with double-threshold comparator and shaping circuit, 200 kHz signal is obtained. Meanwhile, the oscillator with frequency extension by divider circuit generating logic signals to control the expansion capacitor size to reduce the electromagnetic interference and enhance electromagnetic compatibility of the system. The oscillator based on 0.5 μm BICMOS technology library, Cadence and Hspice are used to circuit simulation to get the oscillation frequency of 200.8 kHz under the typical applications. The frequency varies migration range is within ±1% and ±5% floating with temperature changing in -40~125℃.The oscillator has been successfully applied to the design of an AC/DC fly-back power management chip.