With fumaric acid and ammonium hydroxide as raw materials, synthesis of L-aspartic acid by immobilized cells of aspartase engineering bacteria was carried out. The effect of fumaric acid concentration, pH and reaction temperature was investigated. The optimized preparation conditions were as follows: 300 g/L fumaric acid, 37oC, pH7.5, the yield of L-aspartic acid is 96.7%. The immobilized bacteria could be used continuously for 10 times. The aspartase engineering bacterias were distributed evenly over the carrier by electron microscope.The immobilized cells of aspartase engineering bacterias have good stability.