A Monte Carlo model was developed to simulate laser energy transport in biological tissues photon-number-independently and mesh-independently for laser-induced interstitial thermotherapy (LITT). In addition, laser transport characters in human liver tissue and prostate tissue at 1064 nm and 850 nm as well as its main influential factors were analyzed based on the present model. The numerical results showed that the energy deposition depended paramountly on penetration depth in radial direction and on both penetration depth and active emission length in axial direction.