We studied the steering of the nonlocal spatical optical soliton in thermal optical nonlinear lead glass theoretically and experimentally. By employing the conformal mapping method, the response function of the lead glass was obtained, and the influence of the boundary on the response function is discussed. Then we obtained the trajectory for the off-center soliton and the output displacement equation when the point of incidence is varied. We also observed experimentally the phenomenon of steering of the optical soliton in lead glass whose boundary shape is rectangular. The theoretical results are in good agreement with the experimental observations.