This paper proposes a novel family of the legged mobile lander (LML) with multi-loop chains to enable the stationary lander to walk, which is helpful to the Return and Base construction missions in the planetary exploration project. Generally, there are many issues that need to be focused, but one of the key issues is during the landing phase, for which the lander needs to be designed as a truss with ability to bear a large impact, while during the walking phase, the lander needs to be designed as a mechanism with flexible walking ability. To resolve this issue, a novel method for designing a mechanism based on a truss, which also can be called as the truss-mechanism transformation (TMT) method is developed. First, the detailed concept of the same topological arrangements (TAs) of a truss and a mechanism is proposed. Two singularity positions for the truss-mechanism transform are introduced. Second, following the concept, the procedure for designing a mechanism based on the TMT method is presented. Third, some basic knowledge for the creative design of the mechanism is introduced, including the intersection rules of motion characteristics, motion characteristic relationship of multi-loop mechanisms, and so on. Fourth, according to the procedure of the TMT method, numerous novel structures of LMLs with multi-loop chains are obtained. Finally, after the type qualitative evaluation, one typical LML is selected as an example to show its functions among stowed, walking, and orientation positions.