Low gravity is one of the most challenging aspects of robot space exploration. Due to changing gravitational force, the locomotion performance of a legged robot tends to reduce when the gravity decreases. Recently, quadrupedal robots have increasingly been promoted for space exploration. Most existing studies have mainly developed robot locomotion with an erect posture and focused on the use of leg functionality. However so far, the robot locomotion with a sprawling posture and a flexible spine has not been fully investigated. According to this research gap, we present here the sprawling posture robot with a flexible spine inspired by geckos for low-gravity locomotion enhancement. The gecko-inspired robot is constructed with the 3-DOF spine and the 4-DOF legs. The movement of the robot is controlled by a central pattern generator (CPG). The experiments were performed in a physical simulation under the gravities of Earth, Mar, and the Moon. The experimental results show that, due to the lateral bending movement of the flexible spine with a C-Shaped standing wave pattern, the locomotion speed of the robot is increased by 100%, compared to the one with a traditional fixed spine under each gravity. Based on these results, a sprawling-type quadruped robot with a flexible spine will shed a new light for the future study of robot space exploration under low-gravity conditions.