The technology of magnet-assistant pulsed laser deposition was advanced. A magnetic field whose magnetic lines pointed to the substrate was fixed around the silicon substrate when the diamond-like carbon(DLC) film was prepared by pulsed laser deposition(PLD), so that the ions those flied outside of the substrate were drove to fly to the substrate potentially and participate in the course of filming. The concentration of the ions increased based on the centralization of the ions, and the content of the non-electriferous granule reduced indirectly. Compared with the DLC film prepared without magnetic field, not only the deposition velocity of the DLC film prepared under magnetic field increased sharply, but also the mechanical hardness improved. Of the most importance, this research testified to the high efficiency of the ionization by the laser to the target, offering the base of the feasibility to the combinability between the technologies of the PLD and filtration by magnetic field.