The invention discloses a citrinin compound dicitrinone D and an application thereof in respect of malignant melanoma. The citrinin compound dicitrinone D has a structural formula shown in the description. The compound is obtained by culturing penicillium citrinum IBPT-5 through fermentation to obtain a fermented object, and performing separation and purification to the fermented object. It is proved by the experiments that the compound has preferable antitumor activity to human malignant melanoma cells A375, and can be used to prepare a malignant melanoma cell proliferation inhibition medicine or an antitumor medicine, which are used to research malignant melanoma.