With Bayan Obo niobium concentrate and semi-coke powder as raw materials, effect of basicity on melting process of the reduction product of carbon-containing pellets was observed in situ by using a high temperature heat table. The samples with optimum basicity were quenched and prepared at different melting conditions. The migration rule of elements during the melting process was analyzed by SEM-EDS, and the reaction rates of Nb and Si in the melting process were quantitatively analyzed by XRD, TG-DSC and ICP. Results show that with the binary basicity of 1.0, the spattering of molten slag can be effectively suppressed and the melting efficiency can be improved. With the basicity of 1.0 and temperature of 1 350 ℃, the SiO₂ in the slag is reduced at slag-gold interface and pulled into iron phase. After the molten slag is held at 1 400 ℃ for 2 min, the C in molten iron at slag-gold interface is preferentially reacted with the niobium oxide in the slag and reduced to NbC. A small amount of NbC is dissolved into the iron phase, and most of the remaining NbC is wrapped around the granular iron, forming a retention zone, which hinders the mass transfer at the slag-gold interface and reduces the reduction rate. After hot-holding at 1 400 ℃ for 10 min, the reaction rates of Nb and Si are 36% and 1.7% respectively. Titanium and rare earth are not involved in the reaction during the whole melting separation process.