1, find a ball or something with a suitable size, which can completely match the original shape of the hat;

2. Wet the collapsed part of the hat again with water to make it soft;

3. Put the hat on that spherical thing and push it back to its original shape;

4. Wrap the hat in paper, try to keep it in this shape for a long time, and dry it in the shade;

5. Blow-ironing and shaping with a hair dryer at low temperature;