【Objective】 To determine the contents and the existing form of cantharidin in Meloidae. 【Methods】The total cantharidin obtained with acidolysis method and the free cantharidin obtained with direct extraction method were determined in eight species of Meloidae and the control species Huechys sanguinea (De Geer) (Homoptera：Cicadidae) by gas chromatography, and the content of the bound cantharidin in each species was calculated with the content difference between the total cantharidin and the free cantharidin. The relationship between the contents of the bound cantharidin and the contents of Ca and Mg elements in Meloidae were assessed. 【Results】 The results showed that the total cantharidin contents in the samples of Meloidae were 1 to 9 times the free cantharidin contents. The total cantharidin contents were generally higher than 2.0% of dry body weight and the free cantharidin contents were all less than 1.7% of dry body weight in Meloidae. No cantharidin in any form was found in H. sanguinea. Positive relationship was found between the bound cantharidin and Ca element in Mylabris and Epicauta, and between the bound cantharidin and Mg element in Mylabris, but negative relationship was found between the bound cantharidin and Mg element in Epicauta. And the mol of Ca element in Mylabris was lower than that of the bound cantharidin. 【Conclusion】 The contents of the total cantharidin were higher than the contents of the free cantharidin in Meloidae. The bound cantharidin may exist in the forms of magnesium cantharidate and calcium cantharidate.