To establish a method of extraction and contentanalysis by acetylacetone spectrophotometry for formaldehyde in several edible mushrooms.Methods Mushroom samples were extracted by steam distillation with the distillation unit of Kieldahl azotometer instead of direct distillation. Furthermore, the effects of enzyme inactivation, soaking time and temperature on formaldehyde extraction were studied.Results Both in fresh and dried mushroom samples, formaldehyde could be fully extracted in several minutes by direct steam distillation after triturating, and the exact contents of formaldehyde were reflected by the extraction treatment. The linear range for formaldehyde was 0-1 μg/ml, and the method showed good accuracy with RSD＜10% (n=5) and recovery rate ranged from 82.10% to 97.98%.Conclusion The method established in the study is efficient, simple, accurate, precise and suitable for analysis formaldehyde contents in a variety of edible mushrooms.