The study of surface roughness effect on atmospheric stability in Bangkok was divided to four parts, the model sensitivity test, The comparison of meteorological preprocessor model (data from Dunlop site in Birmingham U.K.), The test of surface roughness estimation method with the reference method and the correlation between proportion of particulate matter with atmospheric stability at difference surface roughness length. The result of model sensitivity was found that wind speed and surface roughness effected on friction velocity. Wind speed, temperature, radiation and surface roughness effected on Monin-Obukhov length. The comparison of meteorological preprocessor models was found that RAMMET model gave the best performance compared to the meteorological data at Dunlop site, Burmingham UK. and GAMMA-MET and AERMET also gave a good agreement respectively. However, RAMMET has been limited maximum surface roughness at 1.3 m. Therefore, at the area where surface roughness length was lager than 1.3 m. had to use GAMMA-MET instead. In the third part of this study, Surface roughness estimation method have been compared to reference method, based on wind component and wind profile at Napraran school, Saraburi province and Chulalongkom university. It was shown that the Counihan method gave the best agreement to the reference method. Therefore, the area that had not meteorological measurement on wind component and wind profile, the method of Counihan can be used instead. In the last part of this study, The method of Counihan used to calculate the four areas that had different surface roughness length, Changwattana Road, Ratchadumnum Road, Bangkok Christian School and Sathom Road that had surface roughness about 0.02, 0.88, 1.21 and 9.04 m. respectively. The result of Monin-Obukhov length from GAMMA-MET found that the frequency of atmospheric stability at Changwattana Road and Rachadumnum Road were unstable condition. Bangkok Christian School and Sathom Road were unstable condition about 75% and 50% respectively. The proportion of particulate matter concentration in these four areas found that Changwattana Road was the highest (0.94) and Bangkok Christian School, Sathom Road were 0.91 and 0.86 respectively. The area that was the lowest proportion was Rachadumnum Road (0.65) because the buildings were closely and the roadside of this area had many big trees.