The present paper is a supplementary report on the Opisthobranchia of the Hainan and Xisha Islands. Twenty nine species and 2 subspecies, belonging to 24 genera and 17 families are added. Among them, 18 species are recorded for the first time from the China coasts. Specimens were collected by the Institute of Oceanology, Academia Sinica and South China Sea Institute of Oceanology, Academia Sinica, during the past years. The characteristics of the Opisthobranchia fanna of the Hainan and Xisha Islands may be summerized as follows.