Due to the limitations of the number of satellites, scale and manoeuvrability, it is difficult for the existing earth observation constellations to respond quickly to emergency needs of a high degree of randomness. In order to meet the demand for rapid design of emergency earth observation constellations, an emergency earth observation constellation design method is proposed. Based on the secondary development and coverage analysis function of the space mission toolkit ATK, the method firstly adopts a one-dimensional data hierarchical clustering method to group ground targets, and then applies the differential evolution algorithm to optimize the restricted walker subconstellation configuration for the target groups, and finally generates the restricted hybrid walker earth observation constellation. Simulation results demonstrate that the method can rapidly generate emergency constellations compared with conventional walker constellations and violent optimisation results, and minimize satellite deployment quantity while ensuring the effective completion of the earth observation mission.