Ensuring the safety and efficiency of crane operation is challenging due to the complexity of the lifting operation. The real-time lifting path planning system developed in this paper aims to provide an optimized, collision-free lifting path for mobile crane operators. The first contribution of the developed system is to take advantage of crane mounted sensors and components as the hardware to collect object information. No additional device needs to be purchased. Secondly, the data storage, path planning, optimizing, and visualizing functions are designed to minimize the required computer memory so that the system can be installed and applied on the crane mounted controller for real-time operation. No additional calculation capacity is required. This system has been tested in real construction sites and demonstrated its ability to generate lifting paths satisfying operators' expectation. The system, as an independent software package, can be installed on any mobile cranes mounted with the necessary hardware.