Optical superconducting transition-edge sensor (TES) has been widely used in quantum information,biological imag-ing,and fluorescence microscopy owing to its high quantum efficiency,low dark count,and photon number resolving capability.The temperature sensitivity (αI) and current sensitivity (βI) are important parameters for optical TESs,which are generally extracted from the complex impedance.Here we present a method to extract αI and βI based on a two-fluid model and compare the calculated current-voltage curves,pulse response,and theoretical energy resolution with the measured ones.This method shows qualitative agreement that is suitable for further optimization of optical TESs.