Abstract: This experiment was conducted to study the dynamic variation rule of crude protein content of 15 mulberry varieties for feed use in different growth periods in Chongqing Region. A total of 15 different varieties of two-year-old mulberry for feed use were used as experimental materials, and the crude protein content in their leaves in three different growth stages, including germination period, vigorous growth period and slow growth period were determined, respectively. The results showed that in the germination period, the highest and lowest crude protein content in leaves were observed in the varieties of Chongsang（22.41%）and Yanbiansang 27~#（14.45%）, respectively; in the vigorous growth period, the varieties of Kuisang（20.82%） and Yanbiansang27~#（13.81%） had the highest and lowest crude protein content in leaves, respectively; in the slow growth period, the varieties of Chongsang（19.95%） and Yunnan No.10（19.09%） maintained a higher level of crude protein in leaves, while the lower crude protein content in leaves were found in the variety of Jialing No.16（13.44%）; during the whole growth period, for most of the mulberry varieties, the crude protein content in leaves exhibited an decreasing trend in different degrees, and the most obvious decreasing trend was observed in the varieties of Kuisang, Shuangtouheyebai and Jialing No.16; nevertheless, for the varieties of Yunnan No.10, Dazhonghua, Xinyizhilai, Chongsang and Fengtai, the crude protein content in leaves expressed an elevating tendency from vigorous growth period to slow growth period. Our results provide experimental basis for understanding the dynamic variation rule of nutritional value of mulberry leaves for feed use in different growth periods and implementing scientific and rational feed utilization of mulberry.