The comparison and validation of ozone Standard Reference Photometer (SRP 48) by Institute for Environmental Reference Materials of MEP(IERM of MEP) and SRP 2 by National Institute of Standards and Technology(NIST) are performed in order to establish the metrological traceability. The evaluating the measurement uncertainty of SRP is focused and the main sources of measurement uncertainty are identified. Take SRP 48 for example, the measurement uncertainty components such as the optical path length (Lopt), the pressure (P), the temperature (T), the product of transmittances ratio of the two cells (D) and the crosssection (σ) are calculated, respectively. A measurement mathematical model is established and the standard uncertainty is combined. The results of the comparison show that SRP 48 and SRP 2 are comparable over an ozone mole fraction range of 0~500 nmol/mol. The relationship between SRP 48 and SRP 2 is xSRP48= ［(0.998 96(xSRP2)+0.025］ nmol/mol. The expanded uncertainty of SRP 48 ozone concentration measurement is 2×((0.28)2+(1.10×10－2×x)2) nmol/mol at 95% confidence interval using a coverage factor k=2.