Based on the principle of geometry optics, the confined equations of light propagation in contact laser scalpels are developed in this paper. By use of the Monte Carlo method, the emergent power distribution of the laser scalpels is simulated, the simulation results are consistent with that of the experimental measurements. Different design parameters that effect the emergent power distribution are discussed comprehensively. The simulation results will be benefit for the design of such scalpels and the determination of treatment schemes.