Wire in channel (WIC) NbTi superconducting wire is to let NbTi core wire with small copper ratio embedded into a u-shaped copper channel in high-temperature Tin bath, so as to obtain a NbTi/Cu superconducting wire with a large copper ratio. Results show that emulsifier with the temperature of 50 ℃ and the concentration of 5% can effectively remove the oil and dirt on the surface of Cu channel; Furthermore, the effects of different concentrations of flux "stannous chloride + nitric acid + isopropyl alcohol" on the surface state of core wire and Cu channel. Results show that the surface roughness is very poor after nitric acid fluxing; The surface roughness of the Cu channel is very low after SnCl₂ fluxing, which is very bad to Tinning coating. And "300g/L stannous chloride +15% nitric acid +3% isopropyl alcohol" flux has the best welding effect. Based on the degreasing experiment and fluxing experiment, soldering experiments under different temperature (360 ~ 500 ℃) were conducted. Results show that the surface of wire is not uniform and reveals pink when the soldering temperature is low. When the temperature is too high, the surface of wire is easy to produce tin-lump. When the soldering temperature is ranging from 400 to 440 ℃, wire surface quality is good, without any tin-lump, black spots, burrs, and other surface defects. At the same time, wire bonding force between core wire and Cu channel and residual resistance ratio. can meet the requirements.