Due to the complicated structure of the cast-steel joints of Sunny Valley at Shanghai World Expo Axis, its mass production method faces many problems. In order to manufacture the qualified joints with low cost, high efficiency and high quality, a robot-based manufacturing technology with lost foam process is proposed. With this technology, all joints can be decomposed to standard units. After being cut and assembled by robots, these units can form a complete lost foam joint model used in the lost foam casting process. The cast-steel joints manufactured are measured by three-coordinates measuring machine. Results show that this technology is effective.