Fusarium wilt of banana is induced by Fusarium oxysporum f. sp. cubense. The initial chlorosis symptoms occur progressively from lower to upper leaves, and subsequently occurring in the whole plant. To clarify the pathogenesis mechanism of banana wilt disease, hydroponic experiments with pathogen inoculation were conducted in a greenhouse. The changes of several substances (amino acids, organic carboxylic acids and phenolic acids) in banana seedlings related to the growth of the F. oxysporum were studied. The results were showed as follows: (1) After infection, the injury of banana seedlings was gradually increased. The injury symptom of infected banana seedlings began to be observed at 8^th day, and it was most serious at 16^th day. It showed that height and biomass of the plant were significantly decreased after infection. Compared with non-infected plants, 22% reduction of height was observed in heavy-disease plants. In light-disease plants, 37%, 18% and 23% reduction of dry weight in leaves, pseudostems and roots respectively. The dry weight of leaves, pseudostems and roots was decreased 43%, 21% and 37% in heavy-disease plants, respectively. The water content of both leaves and roots was decreased with the disease development. (2) 16 kinds of amino acids were analyzed in both non-infected and infected plants during the whole infection stage. The total contents of amino acids in leaves were higher than in roots. After the F. oxysporum infection, contents of amino acids in leaves were significantly increased whereas they were decreased in roots. In 16 kinds of amino acids, the contents of serine, valine, histidine, isoleucine and leucine were changed more significantly in leaves under the pathogenic infection, and were respectively increased by 7.1, 6.2, 4.4, 3.5 and 2.3 times in infected leaves compared with non-infected leaves. (3) Oxalic acid, citric acid, malic acid, succinic acid and fumaric acid were detected in both roots and leaves of bananas. Content of organic carboxylic acids were dramatically enhanced in leaves and reduced in roots after the pathogenic infection. Contents of oxalic acid, citric acid, malic acid, succinic acid and fumaric acid in the leaves were increased by 2.6, 1.6, 1.9, 1.8 and 2.3 times after the pathogenic infection, respectively. However, in infected roots, they were decreased to 81%, 42%, 44%, 28% and 59% of the levels in non-infected roots, respectively. (4) Ferulic acid, cinnamic acid and salicylic acid were detected in leaves, while in the roots, hydroxybenzoic acid and eugenol acid were detected. Contents of organic phenolic acids were increased in both the leaves and roots after the pathogenic infection. Ferulic acid, cinnamic acid and salicylic acid contents in the leaves were 2.9, 1.7 and 2.9 times of those in the non-infected leaves, respectively. In infected roots, contents of hydroxybenzoic acid and eugenol acid were 4.3 and 1.5 times of those in the non-infected roots, respectively. It is concluded that the interaction between plants and pathogens could increase the related both beneficial and harmful substances. The banana seedlings have some resistance to injury caused by F. oxysporum infection. However, higher kinds and contents of promoting-bacterium substance than those of anti-bacterium substance leads to disease.