Abstract: The logic controller in original electronic control system of 3C-154 cartoner was made up of discrete components, it was high in cost, poor in reliability, hard for maintenance, and affected regular production.The control system was improved by replacing logic controller with an S7-200 PLC of SIMENS.The circuit design, programming and working principle were discussed.After improvement, electric malfunctions were reduced obviously, operation efficiency was increased, and a lot of maintenance cost was saved.