Abstract: Stability reliability of an existing concrete arch bridge is analyzed using the reliability stochastic finite element method (RSFEM) on the basis of the first order reliability method (FORM). Dead loads, superimposed dead loads, traffic loads and pedestrian loads and the elastic modulus are represented by random variables or random fields. The random fields are discretized using a linear regression discretization method developed by the authors. The limit state function is implicitly represented by finite element stability analysis results. The above procedures and the determination of the gradient of stability eigen values with respect to basic variables are included in the reliability stochastic finite element computer program RESFEP developed by the authors. The analysis gives reliability value of the arch bridge. Sensitivity analysis shows that the elastic modulus of arch ribs affects the bridge reliability most severely, and traffic load has the next severe influence on the reliability.