Abstract: Aim To analyze precision methods for the calculation of reliability under dif-ferent stress and strength distribution . Methods Numerical models applying the com-plete probability method (CPM) are established based respectively on the failure phys-ics and interference theory of stress and strength. The models are then solved throughnumerical integration. Results Equations of reliability in 5 types involving 25 kinds ofparameters (shape, scale and position parameter )and 2 statistical variables (average,standard variance ) realized. Conclusion The CMP is a method of precise theoretical so-lution and it gives high precision solutions in the reliability calculation of mechanicalproducts.