Laser powder bed fusion (L-PBF) enables the integral fabrication of thrust chamber–nozzle and injector assemblies, eliminating some assembly and welding interfaces and reducing structural redundancy. However, under this manufacturing route, as-built geometric deviations act more directly on functional features, creating new challenges for dimensional accuracy and performance stability. To address this issue, this study investigates an additively manufactured 200 N monopropellant thruster and conducts geometric-deviation characterization, deviation–performance mapping, precision allocation, and performance validation. Key forming deviations were characterized using a coordinate measuring machine, industrial CT, micro-focus CT, and confocal microscopy. A first-order geometric deviation–performance mapping model was established through CFD-based sensitivity analysis, and Monte Carlo simulation was used to evaluate performance risk. A priority evaluation system combining the process capability index (Cpk) and performance sensitivity was then developed to guide differentiated finish-machining allowance allocation, CAD model pre-compensation, and process optimization. After two closed-loop iterations, the Monte Carlo-predicted thrust nonconformance probability decreased from 8.5% to 1.2%, and the simulated injection-flow non-uniformity narrowed from ±8.7% to ±4.2%. Cold-flow measurements showed that injection-flow non-uniformity decreased from ±9.3% to ±4.8%. In the rated-condition hot-fire test of the compensated thruster, the measured steady-state thrust deviation was controlled within ±1.5%, while the throat-diameter Cpk increased from 0.56 to 1.45. These results demonstrate that the proposed “inspection–analysis–allocation–compensation” closed-loop method can integrate performance sensitivity with actual manufacturing capability and provide an implementable route for precision-resource allocation and engineering optimization of integrated additively manufactured propulsion components.