An experimental study on the photothermal excitation of bi-layered silicon microresonator is presented. Two methods are used to test the microresonators in the air environment, including the photothermal excitation and electrical sensing method. Corresponding vibration waves of the first three modes are observed in the experiments successfully. By using single optical source, a new method is presented to realize the photothermal excitation and optical sensing at the same time which is more suitable for further application than the traditional two optical sources system.