Abstract: Thermal detector of 10 mW~1 W with SiC ceramic absorbing material and thick film electric heater for excimer laser power measurement is reported. Uncertainty for value reproduce reaches 0.26% (k=1). Laser pulse energy damage threshold of SiC ceramic and other common absorbing materials were studied. Threshold of the cavity used in the detector at 248 nm excimer laser condition is 2.2 J/cm2. Cavity absorbance under different wavelengths was also investigated through integrating sphere system and method for absorbance measurement at 248 nm excimer laser condition is presented. Absorbance of designed cavity is more than 0.99 at tested wavelength. The detector-s opto-electric equivalence was tested based on electric substitute and the unequivalence factor for sensitivity is 1.0026.