The invention relates to a dendritic multi-amino polymer drilling fluid used for mud rock well drilling. The drilling fluid is characterized by consisting of a dendritic multi-amino polymer, drilling fluid bentonite, sodium carbonate, a polymer coating agent, potassium polyacrylate, a hydrolyzed polyacrylonitrile ammonium, a bit balling resistant lubricant and water. The dendritic multi-amino polymer drilling fluid can improve an inhibitive performance of the drilling fluid, can greatly improve the inhibitive performance on clay and drilled chips of the drilling fluid, can reduce plasticity of daub rock, can avoid water-absorption swelling and dispersing of the daub rock, can reduce friction resistance, can prevent bit balling, can increase a penetration rate and can ensure safety of a downhole operation.