Abstract: Objective To observe the effects of different concentration of 17β-estradiol (17β-E₂) on the expression of Caveolin-1 and type Ⅲ collagen in the mouse lung fibroblast stimulated by SiO₂. Methods Fibroblast cells were devided into five groups: blank control group, SiO₂ (100 mg/L) group and SiO₂ (100 mg/L)+ different concentration of 17β-E₂ (10^-8，10^-7，10^-6 mol/L) groups. After treated with different concentration of 17β-E₂, for 48 h, the cells were collected, then the expression of Caveolin-1 and of type Ⅲ collagen were examined with immunohistochemistry method. Results Compared with the blank control group, the expression of Caveolin-1 in mouse lung fibroblasts treated by SiO₂ significantly decreased (P <0.05), While which in the SiO₂+17β-E₂ group significantly increased as 17β -E₂ dose increased (P < 0.05); There were significantly different in the expression of type Ⅲ collagen among different groups (P <0.05), which in SiO₂ group were evidently higher than that in the blank control group, while which in 17β-E₂ groups decreased significantly, when compared with SiO₂ group (P <0.05); 17β-E₂ increased the expression of Caveolin-1 and decreased the expression of type Ⅲ collagen in the dose dependent manner. Correlation analysis showed that 17β-E₂ was positive correlated with the expression of Caveolin-1 (r=0.926, P <0.05), and negative correlated with the express of type Ⅲ collagen (r=-0.914, P <0.05), and the expression of Caveolin-1 and the expression of type Ⅲ collagen was negatively correlation (r=-0.887, P <0.05). Conclusion 17β-E₂ may inhibit the expression of type Ⅲ collagen by up-regulating the expression of Caveolin-1 in mouse lung fibroblast cell to play a role in the resistance of the lung fibrosis.