Objective To know about the formaldehyde pollution in the edible fungi sold in the market of Dongguan in 2005.Method 130 batches of 4 kinds of edible fungi were randomly collected from the 35 wholesale markets of 32 towns of Dongguan,including 56 batches of xiang mushroom,58 batches of tremella,14 batches of Auricularia auricular-judae and 2 batches of Agrocybe aegerita.Results It was found that the positive rate of formaldehyde in the dried xianggu mushroom was 100% and the average content of formaldehyde was 164 mg/kg.It was speculated that two possible factors may be responsible for this case: first,the high background value of formaldehyde in the mushroom;second,the formaldehyde introduced by processing.No formaldehyde was found in the other 3 kinds of edible fungi.Conclusion Many factors influence the formaldehyde content in the edible fungi.Any conclusion during intendance should be made cautiously.