Abstract: The acidizing damage mechanism of horizontal well is totally different to vertical one.On the basis of the flow mechanism,the damage characters of horizontal well are an- alyzed.Generally,the skin factor is used to characterize the damage degree.Skin factors of two different horizontal wells are described and examples are optimized to make a contrast with the discrepancy between the two models.Results show that the skin factor predicted with Furui-Zhu-Hil model is more trustful than that with Frick-Economides model.The effects of the length of horizontal section and the anisotropy coefficient on the skin factor are also presented are also cal- culated and analyzed.