21Cashmere goats, as an important part of animal husbandry production, make outstanding 22 contributions to animal fiber industry. In recent years, a great deal of research has been done on the 23 molecular regulation mechanism of hair follicle cycle growth. However, there are few reports on 24 the molecular regulation mechanisms of secondary hair follicle growth cycle in cashmere goats. In 25 this study, we used transcriptome sequencing technique to sequence the skin of Inner Mongolia 26 cashmere goats in different periods, Analyze the variation and difference of genes in the whole hair 27 follicle cycle. And then, we verified the regulation mechanism of cashmere goat secondary hair 28 follicle growth cycle by fluorescence quantitative PCR. As the result shows: The results of tissue 29 section showed that the growth cycle of cashmere hair could be divided into three distinct periods: 30 growth period (March-September), regression period (September-December) and resting period 31 (December-March). The results of differential gene analysis showed that March was considered 32 the beginning of the cycle, and the difference of gene expression was the most significant. Cluster 33 analysis of gene expression in the whole growth cycle further supported the key nodes of the three 34 periods of villus growth, and the differential gene expression of keratin corresponding to the villus 35 growth cycle further supported the results of tissue slices. Quantitative fluorescence analysis 36 showed that KAP3.1, KRTAP 8-1 and KRTAP 24-1 genes had close positive correlation with the 37 growth cycle of cashmere, and their regulation was consistent with the growth cycle of cashmere. 38 However, there was a sequence of expression time, indicating that the results of cycle regulation 39 made the growth of cashmere change. 40 41 Keywords： Transcriptional group; differentially expressed genes; cashmere goat skin; 42 villus growth cycle; keratin. 43 44 45 49 Mongolia cashmere goats have two distinctly different fibrous structures, with thick and coarse hairs 50 on the upper layer of the skin and fine and soft cashmere underneath. The cashmere comes from the 51 secondary hair follicle structure in the skin[8], and the coarse hair comes from the primary hair 52 follicle structure in the skin[9, 10]. Hair follicles, after shedding old hair shafts, produce new hair 68 was to investigate the correlation between differentially expressed genes and the regulation of hair 69 cycle transitions at different stages of hair growth. The biological functions of differentially 70 expressed genes at different stages of hair growth play an important role in the elucidation of the 71 regulatory mechanism of hair growth, laying a theoretical foundation for the study of this regulatory 72 mechanism. 73 74 Methods 75 Animals 76 In this experiment, Three Inner Mongolian cashmere goats were selected from 77 the same grazing environment. All animal experiments were performed in accordance 78 with the 'Guidelines for Experimental Animals' of the Ministry of Scienc...

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