The invention provides a method for detecting the content of coke powder in delayed coking acid water and a device. The device comprises a measuring cylinder, a sampling bucket, a water storage tank (1), a fiber membrane (4), a suction flask (6), first filtering paper (5), second filtering paper and a clean water bucket, wherein the fiber membrane (4) is connected with the water storage tank (1) through a first pipeline and takes the shape of a rod; the aperture of the first filtering paper (5) is 10mu m; the aperture of the second filtering paper is 1mu m; the volume of the sampling bucket isnot less than 20L; the aperture of filtering holes of the fiber membrane (4) is 10mu m; a conveying pump (2) is arranged on the first pipeline; a second pipeline is connected with one end far away from the first pipeline, of the fiber membrane (4); the first filtering paper (5) is arranged at the top opening of the suction flask (6) and is positioned below the outlet of the second pipeline; a gassuction hole of the suction flask (6) is connected with a vacuum pump (7). By adopting the method and the device provided by the invention, the content of coke powder in the delayed coking acid watercan be accurately detected by people, and the removal efficiency of a coke powder removal process can be analyzed by people in time.