By use of second harmonic generation effect of BIBO (BiB3O6) crystal, laser at 846 nm produced by diode laser is translated into blue light at 423 nm. Calcium atomic beam is emitted from the vaccum Calcium oven when heated up to about 600 ℃. By illuminating the 423 nm laser onto the Calcium atomic beam perpendicularly, fluorescence spectrum of the Calcium beam is obtained with photoelectric detector. The full width at half maximum is about 100 MHz.