Due to the specific characteristics such as rapid strength development, fast setting, and cohesive, magnesium phosphate cement (MPC) is becoming the most widely used materials for the maintenance of existing engineering structures. However, MPC has lower pH value than ordinary Portland cement (OPC). In this case, corrosion is becoming a big challenge for MPC concrete in harsh environment. To investigate the performance of reinforced MPC structures, a group of accelerated corrosion experiments was conducted on reinforced MPC concrete beams under accelerated corrosion conditions. Three non-destructive testing techniques including Half-cell Potential method, Galvanic Current method, and Acoustic Emission technique were employed to monitor the corrosion situation of the reinforcement in the test beams. Based on the measurement results, the effect of magnesium phosphate in the reinforced beam corrosion can be revealed and analyzed. Finally, accelerated corrosion tests of reinforcements in the OPC and MPC concrete beams were conducted to confirm the durability of MPC concrete. From the test results, it can be found that there is an acceptable discrepancy between the corrosion resistance performances of OPC and MPC concrete. Therefore, it can be said that the MPC concrete can be used as an alternative for the OPC concrete in the maintenance of marine buildings.