Batch process is a typical multi-phase process.Due to the interaction between the phases of the batch process,high precision control in a single phase cannot guarantee high precision control of the whole batch process.In order to solve this problem,the guaranteed cost iterative leing control (ILC) of multi-phase batch processes is studied in this paper.Firstly,through introducing the output error,the state error and the extended information,the multi-phase batch process is transformed into an equivalent 2D switched system which has different dimensions.In addition,under the measurable condition,the guaranteed cost iterative leing control law with extended information is designed.The proposed control law ensures not only the stability of the system but also the optimal control performance.Next,in order to study the stability of the system and the minimum running time under the condition of stable running,the multi-Lyapunov function method is used.By means of the average dwell time method,the sufficient conditions ensuring system to be exponentially stable are given in the form of linear matrix inequality (LMI).Finally,the injection molding process is taken as an example to make simulation,which shows the feasibility and effectiveness of the proposed method.