Deformation of the human spine caused by improper sitting posture and other behaviors is prone to induce various diseases. To accurately and timely obtain human spinal deformation data, this paper designs a variable impedance spinal shape trajectory tracking control method based on the gray wolf optimization algorithm. Aiming at the defects of the gray wolf optimization algorithm, such as inadequate position update strategy and easy premature stagnation in optimization, the algorithm is improved from three aspects: population initialization method, position update mode, and global convergence factor. Based on the optimized gray wolf algorithm, the impedance parameters are adaptively adjusted to construct a variable impedance spinal shape trajectory tracking control method. Simulation results show that the improved PGWO algorithm impedance control has the fastest force response speed, smaller stable contact force error, and exhibits good force tracking performance when the environmental stiffness and expected contact force change.