Concerning the existing train break-up and make-up scheme cannot effectively meet the job of stage plan wagon-flow allocating at railway technical station, based on the different hard time window constraints of traction weight and converted length of train, considering constraints of the car flow joining and formation direction, the dynamic wagon-flow allocating model was established by constructing enable-break-up collection, improving the status transition regularity, and updating the pheromone in the ant colony algorithm. The objective of this model was set to maximize the number of vehicles departed and fully loaded departure train. To realize the comprehensive coordination optimization of train break-up and make-up scheme, a decision support system based on ant colony algorithm was designed on the basis of adjustment rules of train break-up and make-up sequence, and by defining a solvable set and improving the status transition regularity and the pheromone update strategy of ant colony algorithm. The result of numerical examples demonstrates that the decision support system can reduce the scale of the wagon-flow allocating problem, effectively help decision-makers choose a satisfactory solution of wagon-flow allocation scheme and get the result of sorting considering marshalling according to the impact of changes in the sequences of train break-up and make-up, so it provides theoretical support for the realization of comprehensive coordination optimization of dispatching system at railway technical station.