Ephemeral plants are an important part of the desert system in China, and slope direction is one of the most important topographic factors in Junggar Desert, which may affect the biomass and stoichiometric characteristics of ephemeral plants in this area. In this study, we detected the biomass allocation and stoichiometric characteristics of different organs (roots, stems, leaves and reproductive organs) of Malcolmia africana and _{Alyssum linifolium}, two ephemeral plants of the Brassicaceae family, in different slope directions (east slope, west slope and north slope) to explore the adaptation strategies of ephemeral plants. The results showed that: (1) the plant biomass of two ephemeral plants was significantly different on different slopes, but the plant biomass of M. africana was the largest on the west slope (1.1±0.0134 g). The plant biomass of A. linifolium was the largest on the north slope (1.45±0.0113 g) and the smallest on the east slope (0.5±0.0084 g). (2) The biomass distribution of M. africana organs was expressed as the leaves > stems > propagating organs > roots, and the proportion of the organs was similar on different slopes. Biomass distribution of organs of A. linifolium was significantly different in different slope directions, and the biomass of roots was significantly lower than that of other organs (P<0.05), among which the northern slope had the largest proportion of reproductive organs, the eastern slope had a large proportion of leaves, while the western slope had little difference in the proportion of root, stem and leaf biomass. (3) Biomass of two ephemeral plants in different slope directions was significantly positively correlated with C, N and P stoichiometry. (4) The N/P values of the two ephemeral plants in different slope directions were all less than 14, indicating that the growth of plants was limited by N. M. africana adjusts its size to suit different environments, while A. linifolium adjusts the proportion of its organs to suit the changing environment. It suggested that ephemeral plants have a strategy to adapt to desert environment by adjusting nutrient and biomass allocation. In the low mountain and hilly areas of Junggar desert, slope orientation is the main environmental factor affecting biomass allocation and stoichiometric characteristics.