It is obvious that investment for a dairy farm can be done through different alternative plans. In this study the decision-making system of choosing the optimal plan from a number of alternatives is considered. The concept of such a system is known as Planning-Programming-Budgeting System (PPBS). There are 4 basic elements in PPBS, namely, (1) objective function, (2) resource restrictions, (3) various alternatives, and (4) comparison among the alternatives. The system developed in this study, is primarily base d on the concepts of PPBS and systems analysis. The optimal solution for each alternative is obtained by the linear programming technique, and the cost-benefit analysis method is used for comparing the results among the alternatives. The special character of the system is that, along with the optimal solution for each alternative, the mutual comparison of the results among various alternatives is performed systematically. The steps for finding the optimal investment plan a n d the flow of the system are illustrated as follows : (1) formulating the investment plan for each alternative, (2) making the input-output table to show the production technological coefficients, (3) finding the elements of resource restriction, (4) deciding the optimal operation level for each process by the linear programming method, (5) considering the appropriate discount rate and economic life of the project and evaluating the benefits and costs by discounting the stream of benefits andcosts at different points of time to get the present values, (6) using cost-benefit ratio as a criterion to decide the feasible plan, (7) checking whether there are still other alternatives ; if there are, start from the step 2 again, and (8) if all alternatives have already been considered, then looking at the marginal cost-benefit ratio and choose the most appropriate one. Based on the above principle, the system was developed by introducing a set of 5 alternative investment plans for a dairy farm. The farmer under consideration is deciding which plan he should adopt for the production, consisting of a certain method and tool as characterized by the different level of investment. The 5 alternative plans are : (I) hand milking, unimproved shed, power tiller, and hand cutting of forage crops, (2) hand milking, unimproved shed, power tiller, and forage cutter, (3) milker, improved shed, power tiller, and forage cutter (4) milker, improved shed, farm tractor, and mower, and (5) pipe-line milking system, improved shed, farm tractor, and mower. Under the assumption of the restricted resource of 72 ares rice field, 154 ares of upland field, 600 hours per month of farm labor, the alternative 4 is proved to be the optimal plan. The basic structure of the system is useful for the Batch Processing method and the Demand Processing method and the Time Sharing System (TSS), which are at present being widely used.