The induction and degradation of certain proteins may occur when plants are exposed to heat stress. However, changes in the amount and composition of soluble proteins in cool-season turfgrasses under increasing temperatures, especially in roots, have not been well understood. This study was performed to determine the critical temperature at which the changes of protein content and components started, and to compare protein profiles of both shoots and roots between two Agrostis species contrasting in heat tolerance. Plants of heat tolerant Agrostis scabra and two cultivars of A. stolonifera, ‘L-93' (moderate heat tolerant) and ‘Penncross' (heat intolerant), were exposed to temperatures of 20, 30, 35, 40, and 45°C in five growth chambers for 3, 7 and 14 days. The results from SDS-PAGE system showed that after experiencing 3 days of heat stress, the shoots of A. scabra had no obvious difference in their protein profiles under all temperatures, while the protein contents in the shoots of both A. stolonifera cultivars were maintained until 40°C but significantly declined at 45°C. Some 54, 57 and 84 kDa HSPs were induced in ‘Penncross' and some 84 kDa HSPs were induced in ‘L-93' at 40°C. Both species showed severe declines in root protein contents at 45°C and some 75 kDa HSP was induced at 40°C. As for the measurements of several other parameters such as chlorophyll fluorescence, chlorophyll and carotenoid contents, A. scabra exhibited the least decline, and L-93 performed relatively better than Penncross under high temperatures. Our results suggest that the temperature of 45°C and 40°C could be critical for protein induction in shoots and roots respectively, while 45°C could be detrimental for both shoots and roots, causing protein degradation, particularly for heat sensitive A. stolonifera plants.