Adjusting and protecting structure for helmet

The utility model discloses an adjusting and protecting structure for a helmet, which comprises a helmet shell, a helmet band and an adjusting device, wherein the adjusting device adjustably connectsthe two ends of the helmet band and is connected with the helmet band together; the helmet shell covers the adjusting device; and the outer edge of a knob of the adjusting device convexly extends outof the lower end edge of the helmet shell. A user can adjust the elasticity of the helmet band by turning the side edge of the knob convexly extending out of the lower end edge of the helmet shell soas to adjust. The helmet shell plays a role in protecting the adjusting device so as to avoid the damage caused by external force to the adjusting device and break the function of the adjusting device, so that the helmet is prevented from loosening in motion and the use safety of the helmet is ensured.