Threedimensional magnetic dipole model is formulated for the stay cable with 95 mm diameter. The magnetic flux leakage field induced by the brokenwire flaw in the 3D space is analyzed. The spatial distribution of the axial component of the leakage field is highlighted and discussed. Scanning system is constructed to measure the axial component of the leakage field. Experimental results verify the accuracy of the magnetic dipole model on leakage field detection. Threshold method is applied to estimate the effective diffusion angle of the axial component of the leakage field along circumferential direction as ±6°, which determines that the minimum number of elements in the sensor array is 30. A circular magnetic flux leakage sensor array is developed for the stay cable. With the liftoff of 8 mm, the sensor array can successfully detect multiple surface brokenwire flaws by providing a scanning image to the cable. The effectiveness of the element number in the array on the quality of the scanning image is discussed. This study provides a reference for designing circular magnetic flux leakage sensor array for surface flaws detection in largediameter stay cable.