The invention relates to a permanent magnetic brushless constant voltage generator and a voltage stabilizing method thereof. The generator is driven by a speed change wind wheel, the sent constant voltage direct current is output to the electric network after the frequency conversion through an inverter, the leakage reactance per-unit value X<*> of an armature winding at the maximum work rotating speed of the generator equals to the ratio of the difference of the maximum work rotating speed and the minimum work rotating speed of the generator to the minimum work rotating speed, and the range of the leakage reactance per-unit value X<*> is from 1 to 1.8. The method increases the leakage inductance value of the armature winding of the generator through the optimized electromagnetic design on the generator per se, so the leakage inductance resistance of the armature winding of the generator in work is increased, the potential E of the generator is in isometric and synchronous change with the leakage resistance voltage reduction X.I of the armature winding when the rotating speed of the generator is changed in the work rotating speed range, and thus, the constant voltage output is realized. The generator can realize the voltage stabilization without increasing any detection and control links, executing mechanisms and the like, the structure is greatly simplified, the cost is greatly reduced, and the invention has the advantages of simplicity, economy, effectiveness and reliability.