Damages correlation of prestressed concrete beam and its safety evaluation have been studied by finite element method. The influences of three typical damages on deflection of beam have been analyzed. The vertical crack damage (VC) has been simulated by pre-crack and contact elements has been set between crack surfaces, the reinforcing steel corrosion damage (RSC) has been simulated by reducing the effective area of the reinforcing steel, and the concrete strength degradation damage (CSD) has been simulated by changing the elastic modulus of concrete based on the relationship between concrete strength and its elastic modulus. Damage correlation variables have been defined, and safety evaluation method of concrete beam based on damage correlation has been discussed. The results showed that: there is a strong nonlinear correlation between VC and RSC, and the beam's safety states are significantly reduced because of the interaction of damages.