This paper presents a real time control method of transportation robot in a production line for its throughput improvement. The robot transports more than thousand works among the processes by one-piece. Furthermore, there are and no buffers between processes in the production line. In this buffer-less production line, blocking phenomenon that a work cannot be transported if there is no vacancy in next process is occurred. For improving throughput of the equipment, both cycle transportation time reduction of the robot and workaround plan for transportation blocking avoidance are required. The focuses of this paper are the throughput balance of multiple processes and the work selection from works waiting same process. This approach realizes a new transportation control system with transported volume balance and shortest path selection. In conclusion, the developed system improves more than 7% throughput from a dispatch method and reaches a high throughput such as optimized by full-search method in 0.2 second calculation time.