Abstract: This study was conducted to determine the efects of diferent 0₃ concentrations (A,8.93×10^-9mol/L;B,4.46 × 10^-9mol/L;C,≤ 4.46×10^-10 mol/L； Control， ambient 03 concentrations were about 1.12×10^-9—1.79×10^-9 mol/L)and diferent exposure last times( gatiIlg 5 d， 10 d，former 15 d，later 15 d and 30 d)at 8.93×10 mol/L oll Chinese cabbage by using 4 farmland open top chambers OTC-1，The results showed that yellow leaf rate increased．daily increase of total biomass decreased an d the ways of assimi．1ation products distribute to organs cha sed with 03 concentrations increase.Leaf number， leaf area， net photo．synthesis of the outer leaves and yield of Chinese cabbage were reduced greatly as the exposure last time at 8.93×10^-9mol/L was prolonged during experiment．And there was little efect to the other leaves. At the same 0₃ concentration(8.93×10^-9mol/L)and exposure last time during diferent growth time of Chinese cabbie．the responses of economy yield and total biomass to 0₃ concentration prophase treatment were nlOl~heavier than that of anaphase．Leaf al a was contrary．But there was no efect to leaf numbers．

Key words: Chinese cabbage(Brassica campestris L．ssp．chinensis), Ozone, Growth, Yield