Sucrose-phosphate synthase (SPS) is one of the key regulatory enzymes in carbon assimilation and partitioning in plants. It plays a crucial role in the production of sucrose in photosynthetic cells. The cloning and expression analysis of a full-length cDNA encoding SPS from tropical epiphytic orchid hybrid Oncidium Goldiana are reported here. The cDNA designated as sps1 is 3820 bp in length with an open reading frame of 3183 bp encoding 1061 amino acids. The deduced amino acid sequence of O. Goldiana sps1 shows 56% and 69% homology with those of maize SPS and spinach SPS, respectively. The high level expression of O. Goldiana sps1 in the flower suggests that it might play an important role in flowering. Growth under higher irradiance and elevated CO2 leads to an accumulation of the sps1 transcript in the photosynthetic leaves. It appears that SPS gene expression in photosynthetic leaves is associated with the leaf photosynthetic rate.