To explore the relationships between the growth of wolfberry fruit (diameter, length and hundred-grain weight) as well as its polysaccharide content and the main meteorological factors, we chose 5-year-old Lycium barbarum Ningqi 1 from 3 main producing areas—Yinchuan, Baiyin and Delingha—as experimental materials and established regression models. The fruit growth curve of L. barbarum in the 3 areas belonged to the double “S” curve: the first growth spurt, the slow periods and the second growth spurt. The growth period of wolfberry fruit from different areas in different development stages differed, as did the whole stage. Polysaccharide content in fruits from the 3 areas always showed a trend of Yinchuan>Baiyin>Delingha. The content of polysaccharide increased with development. Polysaccharide content increased in the slow phase and rapid phase. Average temperature and average temperature difference between day and night were the two main meteorological factors affecting the growth and development of wolfberry fruit. During the whole developmental process, growth rate of fruit from Yinchuan area increased first with increasing temperature and peaked at 23.71°C, 23.93°C and 23.55°C in the 3 periods, respectively, then slowed despite increasing temperature. Growth rate of fruit from Baiyin area continually increased with increasing temperature, and peaked at 22.99°C, 22.16°C and 21.35°C, as did the growth rate of fruit from the Delingha area, with peak temperature 19.55°C, 21.01°C and 20.64°C.