This paper firstly describes the operation plan for freight scheduled-train as a problem of designing service network flow's volume and frequency, by following the basic principles of passenger train transport organization, such as fixed line, fixed operation station along and fixed timetable. Then establish a Generalized Benefit Model which maximizes both time benefit of passengers and economic benefit of trains. Under the guidance of optimal generalized benefit, different analytical formulas are proposed for OD through scheduled-train and multi-group scheduled-train. Finally take Beijing-Shanghai Line as an example, design and evaluate the general operation plan of typical freight scheduled-trains among logistics node cities on the line. The result shows the Generalized Benefit Model has good scientific and applicability for designing freight scheduled-train operation plan.