Diamond Like Carbon(DLC) films were deposited on glass substrates by magnetron sputtering using graphite as the target. The morphology of the films under different nitrogen flow conditions was characterized by atomic force microscopy. Microstructure, valence state of elements and transmittance of the samples were analyzed by Raman spectrometer, X-ray photoelectron spectrometer and spectrophotometer. Results showed that all the deposited films were amorphous. The optical transmittance of the film greatly increased when 2 sccm nitrogen was put in, and the nitrogen content, sp3 bond percentage and ID/IG in DLC film was 5.88%, 64.65% and 1.81, respectively. The optical transmittance of N-doped DLC films in the visible range is about 95.69%. As the nitrogen gas flow rate increased, the optical transmittance of the films decreased. After annealing for 2 h, the optical transmittance of diamond like carbon films with no nitrogen content decreased slightly, while the optical transmittance of diamond like carbon films doped with nitrogen showed little change.