Abstract: Ephemeroid species are an important and special component of the desert flora in China. The Junggar Basin is the easternmost area where the ephemeroid species distribute in arid areas of central Asia. Up to now, there are very few studies on biomass allocation and the allometric relationships of ephemeroid species. Six species, Allium pallasii, Allium caeruleum, Eremurus inderiensis, Gagea nigra and Tulipa iliensis (all belong to Liliaceae) and Scorzonera pusilla (Asteraceae) were chosen as target plants, and about 20 to 35 individual plants of each species were obtained. The One-way ANOVA and Levene’s test were used to analyze the similarity or difference in biomass allocation among six ephemeroid species. The power function was used to test the relationship between the root to shoot mass ratio (R/S) and plant size (aboveground biomass) and between the reproduction allocation ratio (RAR) and plant size of six species using ordinary least squares (OLS, i.e. Model Type I) regression. The reduced major axis (RMA, i.e. Model Type II) regression was employed to analyze the similarity or difference in allometric relationships among six species using SMARTR software. The results showed that the total individual plant biomass of six species ranged from 0.628 g to 21.144 g, root to shoot mass ratios (R/S) ranged from 0.355 to 3.066, leaf to total plant mass ratios ranged from 0.092 to 0.289, and reproduction allocation ratios (RAR) ranged from 0.111 to 0.649. The biomass ratios of reproduction organ and photosynthetic organ were different among six species, indicating that there was no regular pattern of biomass and its allocation ratios among different families, different genera and different species in a genus. R/S of most species declined markedly with the plant body size, while the RAR showed significant increasing tendency with the body size. Most (40 pairs) of the species pairs (45 pairs in total) of organ biomass represented isometric relationships (i.e. their allometric scaling exponents were 1.0), and the aboveground-belowground biomass pairs, leaf-belowground biomass pairs exhibited common allometric scaling exponents (0.8764 and 0.8585) respectively, showing strong functional convergence. However, they did not show the same allometric relationship of six ephemeroid species, which might be due to the difference in the genetic property determined by the taxonomic position.