AbstractGeomagnetic navigation is a new navigation technology and has very important significance for the national defence. Spatial geomagnetic database is a precondition for implementing geomagnetic navigation. Potential field continuation is an effective method for designing geomagnetic database. The integral‐iteration method is a kind of stable downward continuation methods for potential fields. This paper focuses on convergence analysis of the integral iteration method, and proves that the method converges mathematically. This paper also analyses the robust performance of the integral iteration method, and concludes that when observational data contain noise, the noise may be accumulated during iteration. A new wave‐number domain downward continuation method is presented according to the idea of the regulation method and incremental Wiener filter method. Model test shows that the new method is stable, robust and has a short computation time.