Abstract: In the present paper, the author introduces a new laboratory method to study the formation damage from drilling mud, i. e, a damage radius (r_d)permeability (k) model, unique from those applied at home and abroad. By measuring the dynamic mud filtration under the modelled drilling conditions as well as the observation of mud core damage the damage radius and value of reservoir formation permeability restored can be obtained. The skin effect and production ratio are calcalated to evaluate the mud formation damage, which can be compared with the measured skin effect from field testing. The model provides a new approach to study the formation damage.