TH550-NQ-Ⅱ weather-resistant special welding steel wire rod added Ni， Cr， Cu and other alloying elements， there are more quenching structures in the hot-rolled wire rod structure， the quenching structure accounts for about 40%， the mechanical properties of the full length wire rod fluctuate greatly， the tensile strength of the full length wire rod fluctuates above 80 MPa， downstream customers are prone to fracture when directly drawing， and the proportion of broken wires is about 3%. Part of the wire rod needs to be annealed and drawn before it can be used.In order to reduce the quenching structure in the wire structure and solve the problem of the large fluctuation of mechanical properties of the wire rod， the CCT curve of the TH550-NQ-Ⅱ wire rod is measured by thermal dilatation instrument. After analyzing the CCT curve of the TH550-NQ-Ⅱ wire rod， the duplex-phase rolling test of the TH550-NQ-ⅱ wire rod is carried out. The reducing and sizing temperature of the test wire rod was controlled at 820 ℃， and the spinning temperature was controlled at 810 ℃. With the opening of the insulation cover ， the conversion rate of wire rod to F or P is accelerated， the time to complete the phase transition of F and P is reduced， the proportion of hardened structure of wire rod is reduced to about 27%， the tensile strength fluctuation of full length wire rod is reduced to less than 40 MPa， and the proportion of broken wire is reduced to less than 0.5% during customer drawing， which meets the customer's demand for less annealing or non-annealing drawing.