New experimental results are reported on the preparation of molybdenum nitrides by multipulse laser irradiation of molybdenum foils in pure nitrogen atmosphere. In such laser treatment, the laser radiation activates nitrogen and melts the Mo surface, initiating a nitridation reaction in liquid phase. It is observed that there is a significant amount of nitrogen incorporated in the Mo lattice, and that nitrogen is well-distributed in the nitride layers. The nitride layers are found to contain gamma-Mo2N phase and have a microstructure much denser than the microstructure of the original material. Both nitrogen activation and surface melting greatly enhance the creation of Mo-N compound. Successive surface heating and melting and transient shock waves induced by laser pulses could account for the microstructure densification of the nitride layers.