ABSTRACT According to the data of the Taiwan Air Quality Monitoring Network (TAQMN), the suspenden particulates decreases gradually with year at the Kao-Ping Air Quality Area, but the ozone increases with year and deteriorates. Therefore, the problem of the ozone is wating for solving at Kao-Ping Air Quality Area. Because the ground-level ozone has a relationship with NOx and VOC, they are thought to be the major precursors of the ozone. The concentration of the ozone is not linearly related with concentrations NOx and VOC. The precursors of the ozone affect the ground-level ozone, so the photochemical indicators are further developed in recent years. The photochemical indicators H2O2,HNO3 and NOy in this study in Kaohsiung area are analysed by criteria values (Sillman,1995 and 1997) and on-site sampling. The sampling sites are at Nan-Zih, Siao-Gang, Lin-Yuan and Chiao-Tou. The results can determine the major precursors forming ozone. In addition Smog Production Model (SPM) is also used to analyze the results. According to the analyses of the photochemical indicators, Nan-Zih, Siao-Gang, Lin-Yuan and Chiao-Tou are VOC-limited in the spring, summer, fall and winter.According to the analysis result of SPM, the four sites are also VOC-limited in four seasons.