A series of dialkyl α-diazophosphonates bearing different substituents have been prepared from natural amino acids in order to investigate the steric effect in 1,2-migration reaction of metal carbenes. The diazo decomposition of the diazophosphonates using the AgOTf/NaBAr_F complex resulted in β-hydrogen migration to give β-amino (Z)-enylphosphonates in good yields with high regio- and stereoselectivity. A possible reaction mechanism shows that the steric effect could dramatically influence the geometric isomerism aptitude. This new method for constructing (Z)-β-amino vinylphosphonates should be of general utility in organic synthesis.