Disclosed in the present invention are a novel isoindoline derivative, and a pharmaceutical composition and an application thereof. The compound as represented by formula I, and a pharmaceutically acceptable salt, a solvate, a crystal form, a stereoisomer, an isotopic compound, a metabolite, or a prodrug thereof disclosed in the present invention can be used for adjusting generation and the activity of PDE4 or TNF-a, so as to effectively treat cancer and inflammatory diseases.
