Thermal effect has important influence during the stretch blow moulding (SBM) process of PET bottle. Setting the heating condition in an industrial context is a complex task. A 3D simplified modelling of the heating stage during this process is proposed. In this numerical approach, the radiation source is simulated by using a model for intensity of the incident radiation and the Beer Lambert’s law. On the other hand, the ventilation effect under industrial condition is taken into account by a modelling of the forced convection around a cylinder. The IR flux and ventilation effects are implemented as thermal boundary conditions in COMSOL for a 3D computation of the thermal problem for the preform only. Based on this simplified approach to achieve quickly the numerical simulation of the preform heating, an optimization procedure is proposed to adjust the settings of the infrared lamps by comparing our simulation results to the target temperature profile. This optimization tool provides quickly a first set of parameters to help industrial to obtain the desired temperature profile.