Quantum illumination is a quantum sensing technique where entanglement is exploited to improve the detection of low-reflectivity targets in a strong thermal background. In this paper, we study the quantum illumination of suspected targets under the curved spacetime background of the Earth. It is counterintuitive to find that to achieve the same error-probability both target detection scenarios, the illumination strategy curved spacetime consumes less resources than the flat spacetime strategy. That is to say, the gravitational effect of the Earth can promote the efficiency of quantum spatial target detection. This is because the average particle number of the thermal signal reflected in the curved spacetime is always less than the number in flat spacetime. We also find that the spatial quantum target detection with bipartite entangled state is more efficient than the coherent state strategy in the curved spacetime.
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