Abstract: Laser diode (LD) is a current injected device whose characteristic and life are greatly dependent on the performance of LDused current supply. A novel current supply for middleandlow power LD has been designed, which operates on the principles of voltagetocurrent conversion, current amplification,and current negative feedback. A continuously adjustable output current from zero to three amperes can be achieved, and when the output current is two or three amperes, the current variation obtained in an experiment within five hours are smaller than one milliampere, corresponding to the stability of 5.0×10-4and 3.3×10-4. In addition, the current supply has multiple functions such as antisurgecurrent,current interruption protection, overcurrent protection,etc. Compared with the traditional current supply,this device has advantages of simple working principle and high stability, and it will be found wide applications in the fields of teaching, scientific research and production.