Due to the widespread use of pressure vessels in various industries such as refineries, petrochemical industries, oil and gas, power generation, it is important to analyze these vessels in terms of temperature and pressure variant loads. In many applications, the vessel experiences different types of uniform and cyclic loads. Therefore, considering effects of temperature and pressure both individually and/or in combination, on the vessel, are important. In many applications, effects of pressure and temperature are considered as well as compressive pre-stress caused by wire winding process on the vessel. Materials used in the manufacture of these vessels are usually alloy steels, such as high strength nickel-chrome alloys. The material considered in this study was DIN 1.6959 steel. Elastio-plastic stress analyses of the cylinder were carried out under operating temperatures and pressures. To model the real behavior of material and considering Bauschinger effect, different linear and nonlinear hardening models were investigated in this study. Then, simulation of ratcheting in the cylindrical pressure vessel with nonlinear kinematic and isotropic hardening was performed. To use these non-linear mixed models, UMAT subroutines were used in the simulations, and the simulation results of these subroutines used in the material model, were compared with previous experimental results of the same material in published articles for validation. Stress distribution in the cylinder thickness were obtained and compared with each other in various combination types of temperature and pressure, i.e. temperature alone, pre-stress due to wire winding process, internal pressure alone and various combination of all. It was concluded that sequence of temperature, internal pressure loads and wire-winding load is important in the system. For example, average values of Mises stresses in combination load cases due to wire winding and temperature with out internal pressure in the thickness of cylinder is higher than temperature load alone. As a result, it can be concluded that it is necessary for temperature loads to be not applied on the vessel right after applying wire-winding loads. For simulating, finite element software was used and with different combinations of loads using previous situations, stress and temperature distribution were obtained in the cylinder. Obtained results were compared with the available numerical solutions in the literature and a good match was observed. Keywords: Heat transfer, Thick Pressure Vessel, DIN 1.6959, Inside Pressure, Finite Element Simulation, Ratcheting Phenomena, Non-linear Combined Hardening, Non-Uniform Thermal Loads