The invention discloses a method for obtaining cross section through bar material rotary-type cutting and a device for obtaining the cross section through the bar material rotary-type cutting. The method adopts a manner that a bar material and a cutter both adopt active rotations; and, when cutting is performed, the rotary bar material and the rotary cutter contact each other to perform the cutting, and then a cross section is formed through the cutting. The device comprises a rotary clamping mechanism, a cut-off end holding and clamping mechanism, a cutter mechanism and a cutting feeding mechanism; the rotary clamping mechanism is composed of a rack body, a rotary clamp head which is rotatable and is disposed on the rack body, a drive motor disposed on the rack body, and a transmission mechanism connected between the drive motor and the rotary clamp head; and the cut-off end holding and clamping mechanism is composed of a rack body and a cut-off holding clamp disposed on the rack body, the cutter mechanism is composed of a drive motor and a cutter, the rotating axis of the cutter and the rotating axis of the bar material are parallel to each other, and the cutter is disposed at a height between the rotary clamp head and the cut-off holding clamp. The bar material rotating and cutter rotating manner is adopted, and the cross section obtained through the cutting can completely satisfy a high-precision analysis detection requirement.