The photoabsorption cross sections of NO have been measured in the wavelength range 150~200nm, and the cross sections deviation from Beer-Lambert law due to the insufficient resolution of light source is discussed qualitatively. From the steady state approximation of quenching reactions, the pressure dependence of foreign gas on the ratio of absorption intensity to the fluorescence intensity is derived. Furthermore, the non-Stern-Volmer behaviors of the C2£S(n=0) state of NO were discussed by assuming the non-predissociated (J<9/2) and the predissociated (J>9/2) rotational levels following different quenching mechanisms.