Hot deformation behaviors of TC11 alloy with β-annealed larnellar structure and forged equiaxed structure were investigated in the β field in the temperature range of 1 090-1 030 ℃ and strain rate of 0.001-0.1 s-1. By means of isothermal compression tests. Hot deformation characteristics and microstructure evolutions of the two starting structures were analyzed. And hot processing power dissipation efficiency maps were established. EBSD technique was used for testing grain boundary characteristic of deformation structures. The results indicate that hot deformation mechanism of TC11 alloy in β field is dynamic recovery accompanied by geometric dynamic recrystallization at large strains, or discontinuous dynamic reerystallization based on the starting structure states and deformation parameters. Accordingly, there are two different grain refining patterns. One is characteristic of new fine grains in the interior of elongated prior β grains that have serrated grain boundaries; and the other is that of new fine grains along elongated prior β grain boundaries.