Abstract: In order to select a better fit method for the monitoring thoracic particles in air of public place and supply proofs for the establishment of national standard method for hygienic examination of thoracic particles in air of public place.P-5L₂ light scattering dust analyser,LD-1 laser dust monitor and filterpaper weight method were used to monitor thoracic particles at the same time in spring,summer,autumn and winter in four types of public places of Chang zhou area.The results showed that quality ocncerntration and relative concerntration have significant correlation(r₁=0.7787,P<0.001;r₂=0.7526,P<0.001),and the conversion coefficient (K) of relative concentration andquaity concentration was demonstrated approximate normal distribution.The average coefficient of P-5L₂ light scattering dust analyser and LD-1 laser dust monitor were 0.0163,7.42×10^-4 respectively.The conversion coefficient did not vary with type of public place,season and whether using air conditioner or not.The monitoring results were stable.So it is feasible to apply light scattering method instead of filterpaper weight method.And P-5L₂ light scattering analyser and LD-1 laser dust monitor have much compatibility in monitoring thoracic particles in public place.In view of differences of convers coefficient among different areas.Therefore,the conversion coefficient should be measured before using the apparatus.