The invention relates to an improved technology of shape memory alloy, in particular to a high-strength Ni-Ti-Nb-Mo quaternary shape memory alloy and a processing process. Metered by atomic percent, the shape memory alloy comprises the following chemical components: 42-47 percent of Ti, 3.5-8.0 percent of Nb, 0.1-2.5 percent of Mo and the balance of Ni and unavoidable impurities. On the basis of NiTiNb shape memory alloy, the strength of NiTi phases is increased due to the solid solution effect of Nb atoms and Mo atoms through adjusting the atomic ratio of Ti to Ni and the contents of Nb and Mo and adopting a reasonable preparation and heat treatment process so as to prepare the high-strength Ni-Ti-Nb-Mo quaternary shape memory alloy. The austenite yield strength of the shape memory alloy at room temperature can reach higher than 600MPa, the breaking strength can reach higher than 750MPa, the elongation can exceed 20 percent, and the maximum recoverable stress can reach 8 percent. The memory alloy is mainly used for manufacturing connecting pieces and fastening pieces of high pressure resistant hydraulic and atmospheric pipeline systems.