Heat transfer from outer thermal shield to an optical cavity is simplified to a multilevel resistor-capacitor (RC) integrating circuit, which is used to calculate the temperature response of the optical cavity to environmental temperature fluctuations. The temperature response of the optical cavity to the distance between the thermal shield and the optical cavity, the number and the thicknesses of the layers of the thermal shield is discussed based on this method when the mass of thermal shield is fixed. The analysis shows that the temperature response time of the optical cavity can be increased by 2 times as the distance between the thermal shield and the optical cavity is reduced from 40 mm to 5 mm. The temperature sensitivity of the optical cavity to the environmental temperature fluctuations can be reduced by at least one order of magnitude when the number of the layers of the thermal shield is increased from 1 to 3 and the thickness of the inner layer of the thermal shield is maximized. The frequency stability of the frequency-stabilized lasers based on the optical cavity can be improved by the optimized design of the thermal shield of an optical cavity.