Abstract: Ephemerals are a group of plants in arid and semi-arid area. By analyzing weight dynamics of 10 species of ephemerals in Fukang Desert Ecosystem Observation and Experiment Station of Xinjiang, The Chinese academy of Sciences in 1991, the following was found out:1. The weight of most ephemerals greatly changed during their growth and development processes. There was one peak on the growth curves of most ephemerals except for Eremurus anisopteris (Fig. 1) 2. The weight of most ephemerals increased rapidly in May. Their weight peaks took place during the middle ten days of July (Table 2).3. The growth characteristics were evidently different among the species of ephemerals. According to the differences the ephemerals could be divided into three types: perennial vegetative propagation type, perennial vegetative and seed propagation type and seed propagation type (Fig. 2, 3).4. The proportion of fruits to the aboveground weight of ephemerals was obviously higher than that of long life cycle herbage (Table 1). The Lowest was 21.5% and the highest was 77%.5. Weight dynamics of most ephemerals were closely related to their height and phenological phase (Fig.1). The shapes of weight and height growth curves were similar during the earlier period of growth and developnent. The weight of most ephemerals increased rapidly in the period of reproduction.