The invention discloses a head lamp arranged on a helmet. The head lamp arranged on the helmet comprises a lamp head and a power source device. The lamp head is arranged on a helmet connecting seat through a fixed component and a moving clamping seat. The power source seat comprises a battery box. The battery box is fixed to a helmet inserting piece through a clamping ring. The back face of the helmet connecting seat is provided with an elastic clamp. The helmet connecting seat and the helmet inserting piece are provided with a clamping belt groove. The helmet connecting seat is provided with a fixed buckle used for being connected with the helmet. The lamp head is provided with a magnetic control light adjusting ring. The head lamp arranged on the helmet has the advantages of being practical, low in production cost, conveniently arranged on the helmet for using, convenient to illuminate, timely in power supplying, and long in illuminating time.