Abstract: Development of the near backscatter light diagnostic system is important to measuring the stimulated Brillouin and stimulated Raman scatter so that the near backscatter light fraction of the ICF drive laser will be determined. Based on SG-Ⅲ prototype laser facility, a near backscatter light diagnostic system with an ellipsoidal mirror and other relay optics as core elements is designed and implemented on the facility. The whole system is well held and modulated by a portable configuration. Both the optical and mechanical design items are introduced in this paper. According to the experiment results, the system is credible and effective.