Abstract: To increase plant differentiation frequency, calli of wild rice Oryza meyeriana were treated in different methods. Main results are showed as follows. ( 1 ) Low temperature at 4-8 ℃ promoted plant differentiation frequency of long-term calli cultures. The effect was most prominent for 12 day' s treatment. (2) Agarose in place of agar as gelling agent in medium significantly increased green plant differentiation frequency. (3) Liquid-solid alternation subculture was proved as an effective method to maintain embryogenic property of the long-term cultured calli. Green plant differentiation frequency was kept above 41.6% after 18-month alternation culture, while plant differentiation ability was lost after 12-month continuous suspension culture. (4) Variation of esterase isozyme pattern showed that some isozymes bands correlated with the differentiation ability of calli of O. meyeriana.