In this study, visibility observation, aerosol sampling, statistical analysis and model regression were conducted to investigate the influence of suspended particle characteristics and pollution sources on visibility and extinction coefficient in Koahsiung metropolitan area. The scene monitored by a digital camera was then proceeded by digital image processing and were then compared with observed atmospheric visibility observation. Meteorological parameters of various weather patterns (including relative humidity, wind direction, wind speed and mixing height ) played important roles on the reduction of visibility in metropolitan area. Synoptic charts were collected over the 1992-1999 period to analyze their influence on ambient air quality. This study revealed that high PM10 concentration and unhealthful PSI index occurred at weather patterns of high pressure outflow style I and circus-sluice of high pressure outflow¡C Regular visibility was observed during the period of November 1998- April 2000. The highest visibility was above 20 km while the lowest visibility was loss than 1 km in Koahsiung metropolitan area. The observed visibility was mainly distribution over the 2-6 km. The visibility below 6 km were about 61.88% of total observation days and poor visibility was usually occurred in winter. Besides, intensive visibility observation was conducted in January and March, 2000. Visibility was observed hourly at Kaohsiung Meteorological Station and Fa-Shin Temple, respectively. Suspended particles were continuously sampled for five hours at Chien-Chen, Sen-Min and Chien-Gin ambient air quality stations. These measurements were conducted to investigate the influence of chemical and physical properties of suspended particle and meteorological parameters on visibility and extinction coefficient in Koahsiung metropolitan area. Receptor model was applied to understand the emission sources of fine particles (PM2.5) and investigate the influence of emission sources on visual air quality. In addition, the determination of visibility by imagine processing was discussed. Visibility observation was coincided with scene monitoring in order to clarify the relationship between image processing and observed visibility. A illumination eigenvalue calculated by picture transfer software was used to correlate with observed visibility. This study revealed that, illumination eigenvalue and observed visibility had strong negative correlation (R=-0.9079) at effective visual range of 5-10 km. Results form single-factor analysis indicated that no significant variation of aerosol particle concentration was observed at three ambient air quality stations. A bi-mode size distribution of aerosol particles was observed for most stations in Koahsiung metropolitan area. The peak aerodynamic diameter of fine and coarse particles was observed at 0.56-1.0