This study was conducted to evaluate the effect of substrate to inoculum ratio and inoculum type on solid state anaerobic digestion of dairy manure collected from sawdust bedded pack barn. Dairy manure inoculated with different type of inoculum, dairy manure inoculum (DMI) and municipal sewage inoculum (MSI), was digested for 56 days at different substrate to inoculum ratios (SIR) of 0.5, 1, 2, and 4 on volatile solids (VS) basis under mesophilic condition (37 C). Digesters inoculated with DMI showed higher biodegradable volatile solid removal (BVS removal: 52-82%) and methane production performance (P: 32-38 mL g-VS-1) than MSI inoculated test units. However, the maximum cumulative CH4 production was only 38.1 mL g-VS-1, in consequence of a large quantity of non-biodegradable materials included in dairy manure and nutrient losses during long-term storage of dairy manure. To improve the efficiency of methane production, additional studies need to be carried out using fresh dairy manure which has high methane production potential as anaerobic digestion substrate.