Aiming at the synchronization errors between distributed positioning sensors equipped with single antennas, a multi-frequency fusion Direct Positioning Determination(DPD) algorithm based on a single auxiliary source is proposed. Firstly, the received signals are segmented, and the frequency-domain data of the wideband signals are converted into a set of single-frequency signals. Secondly, the synchronization error matrix is pre-compensated using the signals received from the single auxiliary source, and this matrix is then applied to the received data from the target radiation source. Next, the subspace orthogonality relationships under multiple single-frequency signals are fused, and a minimized cost function that separates the unknown attenuation coefficients is constructed using the Lagrange multiplier method. Finally, the target area is divided into a grid, and the radiation source is estimated through peak searching of the cost function. Simulation results validate the effectiveness of the proposed algorithm. Under given parameter conditions, compared with another single-auxiliary-source-based direct positioning algorithm, the computational complexity of this algorithm is reduced by at least 86.91%, achieving better positioning accuracy under different Signal-to-Noise Ratio(SNR) and synchronization error conditions.