A modified molten salt process has been developed to directly synthesise the superconducting Ba1-xKxBiO3. Unlike the other known synthetic procedures in which either the multiple steps are necessary (ceramic method) or the chemical composition and the superconducting properties may depend on various factors (electrolytic method), this process offers several advantages such as low temperature synthesis, single-step reaction as well as easy control of stoichiometry. The superconducting transition temperature of the so-prepared sample with x = 0.4 reaches 30.8 K, among the highest reported in this system. Further. this process may, potentially, be extended to the other related systems.