This paper proposes a model of integrated production, distribution and transportation planning for
4-echelon supply chain system that consists of a manufacturer using a continuous production process, a
distribution center, distributors and retailers. By means of time-dependent demand at all retailers and direct
transportation from one echelon to its successive echelons, the purpose of this paper is to determine
production/replenishment and transportation policies at manufacturer, distribution center, distributors and
retailers in order to minimize annually total system cost. Due to the proposed model is classified as a mixed
integer non-linear programming so it is almost impossible to solve the model using the exact optimization
methods and a lot of time is needed when the enumeration methods is applied to solve only a small scale
problem. In this paper, we apply the genetic algorithm for solving the model. Using integer encoding for
constructing the chromosome, the best solution is going to be searched. Compared with enumeration method,
the difference of the result is only 0.0594% with the consumption time is only 0.5609% time that enumeration
methods need
