An organosilicon quadripolymer of acrylamide (AM), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), N-vinylpyrrolidone (NVP) and a kind of organosilicon monomer was synthesized by solution free radical polymerization. The chemical structure of organosilicon quadripolymer was characterized by Fourier transform infrared (FTIR) spectroscopy, and molecular weight distribution was determinate by gel permeation chromatography (GPC) under the best optimum synthesis conditions, which were identified by orthogonal test according to filtrate volume of fresh water-based drilling fluid. The colloidal properties of the organosilicon quadripolymer drilling fluid were investigated in various media such as fresh-water, 4.0% salt-water, and saturated brine based fluid. The results showed that the filtrate volume decreased with the increase of the organosilicon quadripolymer concentration before and after the thermal aging test at 180 degrees C for 16 h, and the filtrate volume after the thermal aging test was larger than that before the thermal aging test, but was smaller than the base fluid. The colloidal properties and the filtrate volume could be controlled effectively at aging temperatures not exceeding 200 degrees C. The organosilicon quadripolymer drilling fluid performance was better than corresponding terpolymer without organosilicon group and shows favorable inhibitive property and was an excellent fluid loss additive for drilling fluid resisting high temperature in deep wells. A possible mechanism is proposed to explain the improvement according to the comparative adsorption experiment. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 28-40, 2013