Abstract: Variation characteristics of particle size, chemical composition and pollution source of the ambient particulate matter of Tianjin City in 1985,1and 2011were analyzed. The results showed that mass ratios of fine particulate matters to PM₁₀ were gradually increasing, from less than 0.51in 1985to 0.57in 2011. Chemical compositions of PM₁₀ significantly changed, evolved from single crustal elements to multiple crustal elements including carbonaceous matters and secondary particles. The dominant components of PM₁₀ were Si, Al, Mg, Ca for 1985, were TC, Si, SO₄^2-, Al, Ca for 2001and were TC, Si, SO₄^2-, NO₃^-, Ca for 2011, respectively. The change of different chemical compositions has taken on in different styles. The proportion of Si in PM₁₀ decreased sharply first then remained slightly stable, from 28.7% for 1985to 7.6% for 2011, the percentage of carbon component in PM₁₀ decreased slightly, from 24.9% in 2001to 17.9% in 2011, while the concentration percentage of secondary particles (SO₄^2- and NO₃^-) in PM₁₀ remarkably increased from 10.2% in 2001to 18.3% in 2011. The contribution of soot dust to PM₁₀ decreased from 45% in 1985to 22% in 2011, while the contribution of open sources, secondary particles and motor vehicle exhausts apparently increased from 29%, 6% and 3% in 1985to 35%, 16% and 16% in 2011, respectively. Contribution of main sources to ambient particulate matter became more. The type of particle pollution has been changed from soot pollution to mix pollution to complex pollution.