A method for planning physical observation tasks in a space-air-ground integrated sensor network includes: obtaining capability data of available space-air-ground sensors, discretizing a spatiotemporal range of a monitoring scenario, and establishing spatial, temporal, and spatiotemporal mapping relationships between discretized spatiotemporal locations and sensor capabilities; performing quantum encoding on the spatiotemporal locations, sensors, and observation capabilities, and executing a quantum entanglement operation based on the constructed three types of mapping relationships, to build a unified quantum state representation of the spatiotemporal observation capabilities of the space-air-ground sensors; for a specific computation requirement, constructing a corresponding quantum operator and applying a quantum algorithm to perform efficient computation and measurement on the unified quantum state representation to obtain a computation result, thereby enabling scheduling of the space-air-ground integrated sensor network. The inherent bottlenecks in representing and computing spatiotemporal observation capabilities in the classical computation framework are resolved.