How the nitrogen pressure in the chamber influences the diamond-like carbon (DLC) film deposited by pulsed laser deposition (PLD) and its infrared property are investigated. The DLC films are deposited on silicon substrates by pulsed laser when the nitrogen pressure in the chamber is 10-3, 10-2 and 10-1 Pa respectively. The microstructure and composition of the DLC films are detected by the visible Raman spectroscopy and the X-ray photoelectron spectroscopy (XPS). The topography of the DLC films is detected by the atomic force microscopy (AFM). The infrared transmission spectra of the DLC film is detected by the Fourier transform infrared (FTIR) spectroscopy. The experimental results demonstrate when the nitrogen pressure is enhanced from 10-3 Pa to 10-1 Pa, the fraction of sp3 bonded carbon atoms should increase in the DLC films, the fraction of C－O and C＝O should decrease, the size of graphitic crystallites should decrease and the roughness of the DLC films should increase remarkably. At the same time, the infrared antireflection rate of the DLC films should decrease and the infrared antireflection range should become narrow when the nitrogen pressure is enhanced from 10-3 Pa to 10-1 Pa.