LaSi3N5∶Ce3+blue phosphors were prepared by carbothermal reduction method. The influence of C content and heat-dealing on purity and luminescence of samples were investigated. The phosphors were characterized by X-ray diffraction (XRD) and fluorescence spectrophotometer (PL). XRD patterns revealed that LaSi3N5∶Ce3+could be combusted at 1 600 ℃. There was a single-peak broadwide emission spectrum between 380~600 nm due to the electron transfer of Ce3+ from 5d-4f excited by 360 nm. The luminescence intensity reached the maximum value atnC/nLa=4/1 followed by a continuous decline with a red shift and then a blue shift appeared in the spectrum. The luminescence intensity of samples improved 60%~345% after heat-dealing. WLED were fabricated by applying a blend mixture of the sample and commercial YAG on a UV chip (λ blend m), which indicated that LaSi3N5∶Ce3+blue phosphor had a potential application value in WLED.