Abstract: In order to study the alternative splicing status and function of new transcripts of the chicken collagen type Ⅲ alpha 1 chain（COL3 A1） gene, 15-day Guyuan embryo（embryonic stage） and tissues（heart, liver, brain, lung, kidney, and muscle） of 180-day adult（adult stage） chickens were used as experimental samples. Primary myoblasts were isolated and cultured from 15-day chicken embryo tissue samples. Real-time fluorescent quantitative PCR technology, CCK 8 trials, EdU, and flow cytometry were used to identify the new transcript and analyze its expression, so as to study its effect on the proliferation of Guyuan chicken myoblasts. The results showed that a new kind of chicken COL3 A1 gene transcript was found and identified, it was named the chicken collagen type Ⅲ alpha 1 chain-1（COL3 A1-a）. Its expression level was high in embryonic lung and adult muscle tissue. After the expression of COL3 A1-A in Guyuan chicken myoblasts was disrupted, the expression of COL3 A1-a was decreased by 44%（P＜0.05）, which resulted in a significant decrease in the expression of pro-proliferation marker gene PCNA（P＜0.05）, and a significant increase in the expression of anti-proliferation marker gene p21（P＜0.05）. After interfering with the expression of COL3 A1-A for 24 h, the cell viability decreased by 10%（P＜0.05）, the proportion of EdU positive cells was significantly reduced, and the proportion of EdU positive cells was decreased by 10%（P＜0.01）. The proportion of S phase cells decreased and the growth of myoblasts was inhibited. The results indicated that interfering with COL3 A1-A could inhibit the proliferation of Guyuan chicken myoblasts, that was, COL3 A1 could promote the proliferation of Guyuan chicken myoblasts. The study of COL3 A1-A in Guyuan chickens was helpful to elucidate the genetic mechanism of excellent growth traits in Guyuan chickens.