Cyclic loading tests were performed on micro-notched samples of high-strength steel S690QT in air and under cathodic polarisation in a saline solution. These specimens were modelled and their behaviour simulated by finite elements calculations with a combined nonlinear isotropic-kinematic hardening constitutive law. This model can simulate cyclic softening and ratcheting effect of the high-strength steel. Stress and strain fields in the vicinity of the notch-tip were calculated. Results show that a strong dependence of the crack initiation with plastic strain accumulation. Hydrogen assisted cracking mechanism is discussed based on arrangements of dislocations structures.