Abstract:The rhizomes of Cymbidium sinense were incubated in the medium of 1/2MS +BA (1mg L-1) +NAA (1mg L-1) +La3+ (10mg L-1). After incubation for 30d, the rhizomes were used for observating the ultrastructure and development of the chloroplast, ndtochondria and nucleus. The results showed; 1. The development of the chloroplast of the rhizome treated by La3+ was enhanced. There were much more lamellae and osdriophilic granules in chloroplast stroma, and the development of the chloroplast was faster than that of the control. There were little lamellae and larger starch grains in the chloroplast stroma of the control. 2. After treatment with lanthanum, the development of Antochondria was enhanced, and their volume was larger than that of the control. There were more ergastic material in mitochondria stroma of rhizome which was treated with La3+. 3. After treated by La3+, the chromatin in nucleus was increased. The above results showed that there was good effect of La3+ on the development of chloroplast, mitochondria and nucleus in the rhizome of Cymbidium sinense.