The invention is a can-filter structure of an oxygen concentrator, which includes: a first can-filter having filter material; a second can-filter having filter material; and an outlet cover. The first can-filter includes an air inlet provided at the entrance side of the first can-filter and a first conical joint formed at the exit side of the first can-filter, wherein the first conical joint is hollow and at least one recess is provided on the outer surface thereof. The second can-filter includes a second conical joint formed at the entrance side of the second can-filter, wherein the second conical joint is hollow, and at least one engaging hook corresponding to the recess is provided on the inner surface thereof for coupling to the first conical joint. The outlet cover is provided at the exit side of the second can-filter and is coupled thereto by ultrasonic fusion.