The growth, change and succession of desert plants are significant indicators of the ecosystem in desert areas. At present, there are many studies on desert plant monitoring and desert plant spectrum based on fixed time sampling data, but few studies on a long time dynamic spectrum. The spectral discrimination of desert plants is due to the fact that it is affected by the time scale. In this paper, we selected plants which were representative of the desert shrubs—Tamarix ramosissima, Nitraria, Haloxylon ammodendron as samples, aiming at finding out the variation law and interspecific dynamic differentiation characteristics of the three desert plants, which was the basis for the identification of desert vegetation by spatial remote sensing. The spectral data of the vigorous plants were collected during the growing season (5~10 months) in the experiment, and the spectral curves of plants in deferent months were compared and analyzed. Results showed changes of the spectral characteristics and a corresponding phenology of desert plants in growing season. The conclusions are as follows. (1) The reflectivity curves of desert plants are consistent with the green vegetation spectrum. There are obvious peaks and valleys distribution. The slopes and areas of red-edge from large to small were as follows: Haloxylon ammodendron, Tamarix ramosissima, Nitraria. The amplitude of their spectral curve is relatively small, with rapid change. The active period of Red edge parameters is August for Tamarix, October for Nitraria, September for Haloxylon. (2) The spectral changes of desert plants are connected with the plant phenology and climate change. The spectral characteristics are related to the vegetative period, flowering period and deciduous period in the visible band, which are related to fruit period, dormancy period and rainfall in the near infrared band, and related to nutrition period, deciduous period, rainfall situation in the shortwave-infrared band. (3) In July, the spectral curves of three plants’ growth status showed that the spectral reflectance of decaying plant are higher than vigorous one in the visible band and mid-infrared band, while they are lower in the near-infrared band, which is close to the curve of soil reflectance.