Abstract: Content of PH3 in food supplies is determined by external method of gas chromatography promptly and accurately. In this study, FPD and Porapak-Q packed column were used. Good linearity was achived (R²=0.9999) when content of PH3 is between 2.5~25.0 ng/mL. standard addition recovery of PH3 was 91.1% ~95.2 and 96.1%~97.4% when its content was 0.01 μg/g and 0.10 μg/g respectively. Comparing to traditional method, this method is more simple and stable and has been proved as a kind of relible method to determine the content of PH3 promptly, RSD of 6 parallel determinations of the same sample could be as low as 0.9%. Determination limit of this method could amount to 0.001 μg/g depending on the quality of samples.