Acetaldehyde is chiefly prepared using the Raschig process in the industry. However, the reactions in this process are complex, there are many side reactions, and pollution is severe. New acetaldehyde oxime preparation process: The oxime exchange method involves the mixing of ketoxime and acetaldehyde, allowing acetaldehyde to replace the ketone group of the ketoxime in the presence of an acidic catalyst, which yields acetaldehyde oxime through the reaction with hydroxylamine. This process offers a good selectivity and few side reactions. It is environmentally friendly, and can avoid the oxidation of acetaldehyde oxime and waste of raw materials through volatilization, while enabling the further improvement of product quality.