Dynamics of PEO-PPO-PEO and PPO-PEO-PPO at the air/water interface upon thermal Stimulation is studied with a fast surface light scattering (SLS) technique, in terms of the dynamic surface tension recovery relaxation of the copolymer solutions in response to a short-pulsed temperature jump. The characteristic of the surface tension relaxation is examined pertaining to the structure, molecular weight, and concentration of the block copolymers at the air/water interface. The surface tension relaxation time of the copolymer surfactants is found to be monotonically related to the molecular weight of the PEO blocks suggesting that thermal sensitivity in surface tension of the copolymer solutions be due to a conformation change of PEO chains in the copolymers at the air/water interfaces upon the temperature change.