The invention discloses a folding lightweight landing mechanism and relates to the landing mechanism of a lander. The invention aims at solving the problems of large volume, complexity in a buffer structure and high cost of the existing landing mechanism of the lander during the launching process. The folding lightweight landing mechanism comprises a triangular space truss type support, a buffer component, an instrument platform and three landing legs, wherein the triangular space truss type support comprises a triangular support, a star-shaped support, a space truss connecting rod component, three groups of main landing leg connecting components and three groups of auxiliary landing leg connecting components, the triangular support and the star-shaped support are arranged at the upper part and the lower part, the triangular support is connected with the star-shaped support through the connecting rod component, the three landing legs are distributed and connected on the periphery of the triangular space truss type support through the main landing leg connecting components and the auxiliary landing leg connecting components, and the triangular space truss type support is connected with the instrument platform through the buffer component. The folding lightweight landing mechanism is applicable to lander exploration activities for asteroids, comets, the moon, the Mars and the like.