Peak expiratory flow meter(PEFM) is a portable medial device used for home health care of chronic respiratory diseases such as asthma. PEFM adapts spring principle for convenient measurement of expiratory peak flow rate, however linear scale could lead to a substantial measurement e rror. The pre sent study identified inherent er ror of the device by theore tical ana lysis, and accurately measured the error of a patented commercial PEFM. Consistent error was observed mainly due to non-linearity of the flow-to-distance conversion principle, which could be fitted to a quadratic formula with satisfactory accuracy. A simple error compensation technique was accordingly proposed based on quadratic error modeling, which decreased measurement error down to less than 1/3 of before- compensation corresponding to only an error of less than 15LPM over a wide range of flow(100-500LPM). Error compensation table was constructed for convenient use of patients. The present error compensation technique is simple and convenient not only to enhance home health care quality but also for the manufacturers to build more accurate PEFM devices.