Abstract: Abstract: Different concentrations of oligochitosan were used on cucumber seeds and seedlings,the results indi-cated: low conc.of oligochitosan promoted the germination of cucumber, the most optimum concentration of oli-gochitosan was 0.1 mgL-1.low conc.of oligochitosan promoted the growth of cucumber seedlings,the heights of seedlings and the areas of functional leaves were increased significantly(P < 0.05) which compared with ck, the contents of chlorophyll , the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and transpiration rate (Tr)of tobacco seedlings were increased significantly (P < 0.05), while stomatal limita-tion (Ls) was reduced significantly (P<0.05) on cucumber seedlings.High conc.of oligochitosan (100 mgL-1)restrained the growth of cucumber seedlings. the most optimum concentration of oligochitosan for cucumber seedlings was 0.1mgL-1. The effect of using twice oligochitosan was better than using once.