Abstract: Signal Direct Position Determination (DPD) is a novel passive localization technology, which shows superior performance in terms of low signal noise rate adaptability and no parameter association necessity. To adapt to the complex electromagnetic environment, this study proposes a coprime array-based DPD method with single moving observation. Considering narrowband signals as an example, this study first formulates the intercepted signal model, then derives its equivalent model related to the corresponding difference co-array, and finally builds the DPD cost function via spatial spectrum technology. Simulation results show that the proposed method can greatly improve the degree of freedom compared to the traditional DPD with a minor loss of resolution and accuracy when an identical coprime array is used. Meanwhile, compared to the uniform linear array-based DPD, the proposed method shows superior performance in terms of the degree of freedom, resolution, and accuracy of localization.