Prestressed steel strands are key components of concrete structures. Once the prestress loses severely, the structure safety will be threatened. To precisely monitor the stress of the steel strand, a prestress monitoring method is proposed, which is based on the magnetic resonance and the magnetoelastic effect. A dual-coil magnetic resonating sensor is designed, the selection of the test frequency is analyzed, and a stress monitoring system is established. To evaluate the feasibility of this method, stress monitoring experiments are carried out. To be special, the galvanized steel strands and the epoxy-coated steel strands are tested under different design tensions. Experimental results show that the induced voltages change similarly with the tension under different batches of steel strands. The induced voltage nonlinearly is related to the stress. By using the three fit, the goodness of the fitting (R 2 ) is greater than 0. 96. In addition, the test sensitive reaches 0. 064 79% / kN. According to the fitting results and the measured induced voltage, the stress of the steel strand is calculated. When the tension is high, the test error is almost less than 4% . This demonstrated that a new stress monitoring method is proposed for prestressed steel strands.