The invention discloses an auxiliary supporting device for a gastrointestinal tumor surgery anastomat. The device comprises a protective clamping shell I and a combined sleeve ring, wherein a protective clamping shell II concentric with the protective clamping shell I is arranged on the outer side of the protective clamping shell I, and a spacing is reserved between the protective clamping shell Iand the protective clamping shell II, and thus organs and tissues can be sutured through the gap between the protective clamping shell I and the protective clamping shell II during the gastrointestinal tract suture surgery, so that the suture stability between the tissues is increased; the design of a cross-shaped reserved opening can help the anastomat to pass through the space, and is stable, so that the device is convenient to improve the efficiency of gastrointestinal tract surgical suture; the protective clamping shell II and the anastomat can be connected together to pass through the interior of the gastrointestinal tract to be sutured, and clamping blocks are attached to the inner side surface of the combined sleeve ring, so that the problem of difficult surgery caused by easy slippage of the gastrointestinal tract is avoided; support rods can rotate to spread the tissues of the gastrointestinal tract, so as to help the suture point to be clearly observed by doctors; and a connecting sleeve and two connecting rods are in threaded connection, so that the spacing between the two support rods can be adjusted.