Abstract: Objective: To compare the effects of two kinds of β₂-receptor agonists and different inhalation devices on the result of bronchodilatation testing.Methods: One hundred patients with bronchial asthma were divided into 3 groups:30 patients in group A inhaled terbutaline aerosol via PMDI,30 patients in group B inhaled salbutamol aerosol via PMDI,and 40 patients in group C inhaled terbutaline aerosol by spacer.The pulmonary function was checked after 15 minutes;the improving rate,the increased absolute value and the positive rate of bronchodilatation were calculated.Results: As for the improving rate,the absolute value and the positive rate of FEV1,no differences were detected in Group A and Group B (P>0.05);in Group C the above three rates were averagely higher than those in Group A and B,and the difference was significant (P<0.01).Conclusions: The comparative study shows that the effects of two short acting β₂-receptor agonists are similar to salbutamol in bronchodilatation testing;the effect of inhaling by spacer is better than by PMDI,as it can increase the absorption factor,enhance the positive rate of bronchodilatation and reduce the missed diagnosis of bronchial asthma.