Method for preparing crystal form FIII from piracetam crystal form FII

The invention provides a method for preparing a crystal form FIII from a piracetam crystal form FII, which comprises the following steps: by taking piracetam crystal form FII as a raw material, adding an alcohol solvent, heating the piracetam crystal form FII until the piracetam crystal form FII is completely dissolved, and preserving heat and stirring at the temperature; then the cooling process from the first stage to the fourth stage is started in sequence, heat preservation stirring is conducted after cooling of all the stages, and the cooling range of the first stage is 5-10 DEG C lower than the complete dissolution temperature in the step (1); the cooling range of the second stage is 10-15 DEG C lower than the cooling temperature of the first stage; the cooling range of the third stage is 20-30 DEG C lower than the cooling temperature of the second stage; the cooling range of the fourth stage is 25-40 DEG C lower than the cooling temperature of the third stage; and then filtering, ...