The invention discloses a secondary throttle device of an engine, which is used for secondary control on the basis of the single stroke control between an idle speed position limit and a full load position limit of an engine throttle handle. The secondary throttle device comprises a stepping motor, a rotary rod and a control handle, wherein one end of a part of the rotary rod contacting a throttle limiting screw is in an elliptic shape, the rotary rod is passed into the control handle and the throttle handle and can rotate relatively to the control handle and the throttle handle, and the other end of the rotary rod is connected with the stepping motor; and when secondary control is in need, the stepping motor starts to drive the rotary rod to rotate, the elliptic part of the rotary rod applies an acting force to the throttle limiting screw during the rotation process, and the throttle handle and the control handle move toward the inner side of a limiting point under the counter acting force of the throttle limiting screw, thus achieving secondary control of the throttle. Through the additional installation of the secondary throttle device disclosed by the invention, the engine performance can be optimized, and the power performance and economic efficiency of vehicle traveling are remarkably improved.