The invention discloses a steering system of a small double-propeller unmanned surface vehicle. The steering system comprises a stepping motor, a coupling, a screw rod, a shaft end cover, a screw sleeve, an intermediate connecting rod, a parallel connecting rod, two propellers, two angle sensors and a bottom control box, wherein rotation of the motor can be converted into translation by using thescrew rod and the screw sleeve; the rotation of the connecting rod can be synchronously converted into rotation control of a left rudder angle and a right rudder angle through action of a parallel mechanism. The steering system realizes synchronous control of double rudder angles in mechanical structure, makes a double-propeller controlled ship body more flexible, can avoid damage to subsequent systems when an over-limit problem in limitation of a whole structure by the screw rod and the screw sleeve and a front-end limit problem in force transmission occur; in addition, control components ofthe system only adopt a single stepping motor, so that the steering system is convenient to operate and simple to control; a control mode of the system is closed-loop or semi-closed-loop control, so that the steering system has characteristics of high stability, strong operability and good safety.