In order to study the spectral radiation characteristics of laser molten pool in laser cladding, grating spectrum detection technology is used to detect the spectrum of molten pool in nickel silicon boron alloy powder laser cladding, spectral distributions in different powers, speed and time are obtained. It is shown that at the wavelength of 550 nm spectrum relative strength is 500 when power is 900 W, and it increases to 600 when power becomes 1000 W, keeping power constant, spectral radiation intensity decreases when scanning speed increases but increases with time and achieves the stable state after 15 s. There is a certain relationship between the quality of laser cladding layers and spectrum fluctuation of molten pool. The results show that when power is 900 W and scanning speed is 2 mm/s, the quality of laser cladding layers is better, the body has small deformation, and the fluctuations spectrum relative strength of the molten pool is relatively little.