Allelochemical production by plants can affect the growth of adjacent plants. In this study, an experiment was conducted to identify some secondary metabolites through the standard procedure of phytochemistry in the dominant species of Artemisia sieberi Besser prior to the flowering stage from the rangelands of the eastern regions of Golestan Province. All the parts of the selected plant were soaked in 10% ratio of distilled water for 72 h. Then, the allelopathic activity of various concentrations including 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100% of the studied plant on the germinating (radicle elongation, shoot and seedling, seed germination, rate of germination and vigor index), physiological (chlorophyll a, b, total) and biochemical (total phenols) parameters of the seed of Agropyron elongatum were examined. This experiment was performed in order to set a completely randomized design with three replicates. Qualitative analysis detected and confirmed some allelochemicals such as saponins, terpenoides and tannins. The results of ANOVA showed that there were statistically significant differences between different concentrations of aqueous extracts among all the studied parameters (P>0.01) except for radicle length. Comparison between the mean concentrations indicated that the treatments have a greater inhibition effect on the germination percentage and germination rate, compared to seedling growth. The effect of various aqueous extracts (except for the 10 percent concentration which caused a stimulation effect on the aforementioned parameters) on the vigor index, chlorophyll a, b, and total indicated significant inhibition processes as the concentrations increased.