<p>The stator flux (SF) initial value of permanent magnet synchronous motor (PMSM) is determined by the initial position of the rotor, so permanent magnet synchronous motor direct torque control (DTC) system requires initial rotor position information to determine the initial value of the stator flux. This dependency can increase system complexity and introduce potential errors when accurate rotor position sensing is unavailable. To solve this problem, this paper proposes to eliminate the initial flux error by constructing the reduced-order stator flux observer (RSFO). So, the PMSM-DTC system operation is not dependent on initial rotor position information. Based on the mathematical model of the PMSM, the reduced-order observer’s structure is formulated, and its convergence conditions are derived to ensure stability and accuracy. The RSFO is then applied within the direct power control system. Results from theoretical derivations, computer simulations, and experimental tests confirm that the proposed observer can rapidly eliminate the initial flux error, achieving accurate flux estimation within a short response time. Importantly, the method allows stator flux observation without requiring prior knowledge of rotor position, thereby simplifying system design and improving startup performance.</p>