Preparation method of agomelatine I crystal form

The invention discloses a preparation method of agomelatine I crystal form. The preparation method comprises the following steps: heating and melting agomelatine at the temperature of 110-200 DEG C, then quickly cooling at the temperature of minus 20-30 DEG C and standing till crystallization. The method used by the invention is simple to operate, reaction conditions are easy to control, the yield is high, any organic solvent is not required, and the obtained crystal form is single, green, environment-friendly and very suitable for industrial production.