Abstract: The processes of flower bud differentiation in Phalaenopsis，cultivar‘V31’，was investigated，and changes of C/N，nucleic acid，and some other metabolites contents in the leaves were also investigated. The results showed that the process of flower bud differentiation could be divided into six phases，initial differentiation，inflorescence primordium differentiation，flower primordium differentiation，sepal primordium differentiation，petal primordium differentiation，column and pollinia differentiation. The contents of soluble sugar，starch and soluble protein in the leaves reached a peak at 35 d after low temperature treatment，and two peak periods of C/N value appeared at 15 d and 30 d. Changes of total nucleic acid content were similar to RNA content，which increased continually since 15 d after treatment，then gradually declined in the phase of column and pollinia differentiation，while the change of DNA content was gently. It was suggested that a high level of C/N be conducive to flower bud differentiation of Phalaenopsis，and the sharp increase in RNA/DNA value（mainly RNA synthesis）was closely relatedto the processes for physiological differentiation shift to morphological differentiation of flower bud.

Key words: Phalaenopsis, flower bud, morphological differentiation, C/N, nucleic acid, metabolite