A series of novel 1,2,4-triazolo[1,5-a]pyrimidine derivatives containing an α-amino phosphonate moiety were designed and synthesized by the multi-step reactions. Their structures were clearly confirmed by spectroscopic data (IR, 1H NMR, 31P NMR, MS) and elemental analysis, compound was further determined by X-ray diffraction crystallography. The results of preliminary bioassay indicated that some of the title compounds possessed moderate herbicidal activities against dicotyledonous plants (Brassica campestris L) at the concentration of 100 mg/L. For example, compound possessed 92.0% inhibitory activity against B. campestris L and showed better activity than that of the commercialized herbicide Bispyribac-sodium; however, compounds displayed weak herbicidal activity at the concentration of 10 mg/L. J. Heterocyclic Chem., (2010).