The cable force in arch bridge hangers is a critical indicator of structural safety. However, due to the structural characteristics of grouted steel-sleeved hangers, conventional monitoring methods such as the frequency-based method, pressure sensor method, and fiber Bragg grating (FBG) method are often inadequate for accurate measurement on such bridge structures. To address this challenge, a detection solution based on magnetoelastic effect sensors was proposed and validated for applying the magnetoelastic effect to these complex structures. The effectiveness of the magnetoelastic method was investigated through theoretical analysis of sensor measurement, magnetic simulations, and laboratory calibration. For the first time, the attenuation effect of steel sleeve thickness on the internal magnetic field was quantitatively revealed. Through laboratory static load tests, it was found that the presence of steel sheaths can reduce the full-scale error of the designed magnetic flux cable force sensor from 2.12% to 4.48%, but still within the engineering standard range of 5%. In engineering applications, the magnetic flux sensor has good measurement repeatability, with a measurement standard deviation range of 11.94~31.3 kN. The measured cable force of the suspension rod shows an increasing trend from the edge to the inside, which is consistent with the normal distribution law of cable force of the arch bridge suspension rod. The results verified the effectiveness and advantages of the magnetic flux method in detecting the tension of large-diameter steel sheathed suspension rods, providing engineering practice reference for health monitoring of similar bridges.