Anaerobic digestion of chicken manure (CM) with high-solid content is typically constrained by ammonia nitrogen accumulation, which influences the microbial activity and methane yield (MY). A strategy of recycling stripped biogas and co-digestion was developed to reduce ammonia nitrogen accumulation and increase MY in a semi-continuously-stirred tank reactor (semi-CSTR) using CM as feedstock (total solid, 10%). The experimental results demonstrate that the stripping strategy can improve hydrolysis efficiency and reduce total ammonia nitrogen, free ammonia nitrogen, and total volatile fatty acids concentrations by 11%, 14%, and 20%, respectively. The soluble chemical oxygen demand (SCOD) removal efficiency and MY were improved by 23% and 37%, respectively compared to the no-stripping operation. In the integrated in-situ ammonia stripping with co-digestion study, with the addition of co-substrate (glucose, sunflower oil, and peptone), which was optimized by a central composite design (CCD) model, resulted in increased biogas yield and MY yield by 39% and 21% over the no-stripping method. The process also evidenced a lower TVFA concentration than the control, inferring the efficient conversion of metabolites towards methane production. This technology could be utilised in high-ammonia waste/wastewater digestion.