Rice straw bales and fresh pig manure were used as feedstock, and added microbial fortification agent and stepwise spraying methods were used to investigate the effect on the gas yield characteristics and fermentation properties of garage-type anaerobic solid-state fermentation at ambient temperature. The test results showed that the added microbial fortification agent advanced the arrival time of the peak temperature by one day and increased the average fermentation temperature by 8.28%. The microbial fortification agent can increase gas production and the time of first yield peak and shorten the start-up time. The maximum gas yield of the enhanced groups was 13.01% higher than the ordinary groups, and the methane concentration increased 16.98%. After the second gas yield peak, the reduction of spraying frequency had almost no effect on the gas yield. The stepwise spraying method was helpful to improve the moisture distribution and the degradation rate of the middle layer. This study provides a basis for evaluating and improving the operating efficiency of the anaerobic solid-state fermentation systems.