A transparent computer-controlled multizone furnace is used to study the interface control of the vertical Bridgman crystal growth. Sodium nitrate is chosen as a model material. The effects of heating profiles and growth speeds on the interface shape during steady-state growth are illustrated. It is observed that the growth front becomes more concave with the increasing growth speed and with decreasing axial temperature gradients near the growth front. When a suitable combination of the growth speed and the heating profile is used, a flat or slightly convex interface can be easily obtained. Numerical simulation is also conducted, and the calculated interface shape and position under various growth conditions are in good agreement with the observed ones.