Compared with vertical wells, the damage zone near the horizontal wellbore will be more complex and calculating the skin factor of horizontal wells accurately will be of great importance. The author considered the non-uniform distribution of damage zone and its anisotropy, combined the infinitesimal method, substitution of similar flows method and law of equivalent percolation resistance, eventually getting a simple and new model to calculate the local skin factor and total skin factor of horizontal well. Case study shows if we can consider the damage zone radius decrease as a combination way between concave way and linear way, the result by new model can have a small relative error with that calculated by method of transient well test. Parameter sensitivity analysis indicates as the increasing of depth of damage zone, the local skin factor and total skin factor also increase, while as the increasing of permeability of damage zone, the local skin factor and total skin factor decrease.