The present subject matter relates to a protecting agent composition for high/ultra-high permeability reservoirs, consisting of a protecting agent and a filler, wherein, the filler comprises calcium carbonate of 600-1,000 mesh, calcium carbonate of 300-590 mesh, and calcium carbonate of 50-200 mesh at 1:(1-30):(0-40) weight ratio, and the protecting agent comprises structural units denoted by the following formulae (1), (2), and (3). The present subject matter further provides a drilling fluid containing the above-mentioned composition. The present subject matter further provides a use of the drilling fluid for drilling in high/ultra-high permeability reservoirs. The drilling fluid provided in the present subject matter has advantages including easy use, high environmental friendliness, and outstanding reservoir protection, greatly reduces the damages of drilling fluid to high/ultra-high permeability reservoirs, and brings substantial economic benefits.