According to the present invention, plant choline monooxygenase and the gene thereof are provided. The present invention discloses the following recombinant proteins (a) and (b) as well as genes encoding the proteins:(a) comprising the amino acid sequence shown in SEQ ID NO: 2, 4 or 6;(b) comprises the amino acid sequence shown in SEQ ID NO: 2, 4 or 6 having deletion, substitution or additon of one or several amino acids, and which has choline monooxygenase activity.