The bake-hardening (BH) values and the "internal friction-temperature" spectrums were studied for the baked 0.11C-1.67Mn-1.19Si TRIP (transformation induced plasticity) specimens with 0%, 2% and 6% prestrain. Results show that the experimental TRIP steel deserves good bake-hardening ability and Cottrell atmosphere is the reason for its bake hardening characteristic. It is also concluded that both the number and the saturation degree of Cottrell atmosphere might affect the BH value of TRIP steel.