This paper systematically described the biological properties of Scatella tenuicosta for the first time. The experiment result indicated that when temperature was set 20 °C from 7 am to 19 pm and 16 °C from 19 pm to 7 am, rhythmically across light day and dark night with 90% relative humidity, the development process of Scatella tenuicosta was as follows, egg period 2.8±0.7 d, larvae period 15.7±1.9 d, pupa period 4.5±1.5 d. The lifetime of adult male generally lasted 4 d or 5 d, the adult female 14-17 d, the longest even up to 22 days, including 14 day-long oviposition period. During the growth period of watermelon grafted seedlings (December to next March), 1 or 2 generations of Scatella tenuicosta would harm the seedlings, and 5 or 6 generations throughout the whole year. Besides, high temperature and drying environment would be conducive to the occurrence and threatening of the Scatella tenuicosta.