Abstract: The patterns and cycles of sexual masturbation behavior of one captive male baiji, "Qi Qi", were reported in this paper. The patters of the behavior consisted of ventral contacting with pond bottom, ventral contacting with pond wall and spreading out of penis. The variation of sexual masturbation behavior seemed to follow a seasonal pattern. The ventral contacting with pond bottom occurred monthly all the years. The ventral contacting with pond wall and spreading out of penis did not occur monthly, but apparently had two peaks one year and the peak in spring was higher than one in autumn. These cycles of sexual masturbation behavior were considered to be indicatives of sexual activity. The occurring sequence of sexual masturbation behaviors was the ventral contacting with pond bottom, ventral contracting with pond wall and spreading out of penis in a period of year.