method and device for blow molding containers , wherein a preform made of a thermoplastic material is shaped to give a container using blow molding pressure in a blow mold once the preform has been subjected to a thermal conditioning step in the region of a heating section along a transport path , and wherein at least one parameter characterizing the blow molding process is measured and supplied to a control device which acts upon at least one adjusting element to change at least one parameter influencing the blow molding process . the control device calculates at least one property of the finished blow - molded container based on the measured parameters characterizing the blow molding process and using a simulation model and compares said property with a set value . based on a possible deviation between the set value and the actual value , the parameter influencing the blow molding process is changed such that a possible remaining deviation is minimized .