The exergy values of three oat straws were investigated. The effects of moisture content, ash content, S content, correlation factor (C, O, H, and N), and lower heating value (LHV) were also studied. The results showed that the moisture-related exergy, ash-related exergy, and S-related exergy varied in the ranges of 283.630-337.502, 28.474-111.054, and 4.357-13.944 kJ/kg, respectively. They accounted for 1.346-1.661%, 0.164-0.538%, and 0.021-0.068% of the exergy of oat straw, respectively. The O/C, H/C, and N/C atomic ratios varied in the ranges of 0.7042-0.7780 (10.480%), 1.4713-1.6000 (8.747%), and 0.0024-0.0254 (958.333%), respectively, whereas the correlation factors varied between 1.131 and 1.142 (0.973%). The exergy values of the three oat straws were between 20.325 and 21.065 MJ/kg. They were mainly determined by the correlation factors and the LHVs. A positive linear relationship between the exergy and LHV was observed.