As a drug for treatment of liver diseases, ornithine aspartate has very wide application clinically. However, existing ornithine aspartate preparation methods consist of: taking ornithine hydrochloride as the raw material, using ion exchange resin to remove chloride ions, then employing ammonia water to conduct elution, carrying out heating to remove ammonia, and adding aspartic acid to perform salification, and have the disadvantages of great time consumption, high cost, large acid-base consumption, great pollution, instability of L-ornithine under an alkaline condition during heating for ammonia removing, and easy generation of impurities. The method provided in the invention includes: adopting ornithine hydrochloride as the starting material, employing an electrodialysis method and making use of the principle that charged ions move under a current function to remove chloride ions in the ornithine hydrochloride, adding aspartic acid to perform salification, and conducting refining with methanol or ethanol. The method not only guarantees the stability of L-ornithine, has the characteristics of simplicity, practicability, and low cost, but also substantially alleviates the environmental protection pressure due to less acid-base consumption, and improves the production capability, thus being suitable for scale-up production.