In order to improve the efficacy of phototherapy for neonatal jaundice, we design and develop a neonatal jaundice phototherapy light source by spectral matching technology. In order to study the degradation of bilirubin, we use the designed special blue LED source, the ordinary blue LED source, the traditional blue source, and the white LED source to irradiate standard bilirubin solution in vitro with concentration of 130.932 μmol/L for 1 h, 2 h, 4 h and 8 h, respectively. The results show that the blue LED light source and the traditional blue light source have obvious degradation effect on the bilirubin solution, and the designed special blue LED has the best degradation effect. The key factor of phototherapy for neonatal jaundice is the spectrum of the light source,and the designed special blue LED can effectively reduce the concentration of bilirubin in vitro.