The aim of this study was to evaluate the effect of degraded polysaccharide of Acanthopanax senticosus (ASPS-1) on the immunological effects and appropriate dosage of broiler chicks with a view to developing a new feed additive. For the experimental design, 180 broiler chicks were randomly divided into six groups, ASPS-1 low, medium and high dose groups, undegraded Acanthopanax senticosus polysaccharide (ASPS) low and medium dose groups and blank control group. The drug was administered for 21 consecutive days, and the growth and data of immune organ index and immune factors were recorded on the 7th, 14th and 21st d. Finally, the effect of ASPS-1 on the intestinal flora of broiler chicks was investigated by high-throughput sequencing of the 16S rRNA gene and the correlation between the main flora and intestinal indexes was analyzed, and the function of microbial community was predicted by using PICRUSt2. The results showed that the addition of high dose of ASPS-1 could promote the body weight growth of broiler chicks, had no significant effect on immune organs, significantly promoted the increase of intestinal villi and crypt ratio, and effectively regulated the levels of serum antioxidant factors and immune indexes. Analysis of the intestinal flora showed that ASPS-1H promoted the proliferation of Lactobacillus, Faecalibacterium, Negativibacillus, and Eubacterium and inhibited the colonization of Desulfovibrio and Turicibacter, and that proliferation of Faecalibacterium, Negativibacillus and Eubacterium was associated with the development of intestinal villi. Predictive analysis of PICRUSt2 function indicates that proliferation of Lactobacillus, Faecalibacterium, Negativibacillus and Eubacterium functions through amino acid metabolism, global and overview maps, replication and repair pathways function. In summary, the addition of high doses of ASPS-1 can improve the immunity of broilers and has the potential to be used as a feed additive.