As an indispensable raw material for green energy, securing an adequate supply of lithium has become a worldwide policy. However, the difficult separation of the homologous elements lithium and potassium severely hinders the efficient extraction of lithium from lithium minerals. Current research provides an industrialization promising technology, the highly selective precipitation of potassium through the jarosite process, for the separation of potassium from lithium-bearing solution. The conditions for precipitating potassium in the jarosite process without or with seed were optimized. Results showed the precipitation ratios of potassium and lithium at optimized conditions are 99.17 % and 0.43 %, respectively, corresponding to a selectivity coefficient (${\text{S}}_{\text{K}}^{\text{Li}}$) as high as $28.00\times {10}^3$. The effectiveness of the jarosite process in selective precipitating potassium is barely influenced by the initial concentrations of lithium and potassium. Adding seed enables the separation of lithium and potassium at lower temperatures with a faster speed in a broader pH range. Compared to some other separation technologies, both the jarosite process without or with seed can achieve significantly higher ${\text{S}}_{\text{K}}^{\text{Li}}$ in a shorter time. Overall, the jarosite process is an effective and commercially promising technology for separating potassium from lithium-bearing solution, favoring the sustainability of the lithium industry.