Background Each GECAM satellite payload contains 25 gamma-ray detectors (GRDs), which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts (GRBs). GRD was designed using lanthanum bromide (LaBr 3 ) crystal as the sensitive material with the rear end coupled with silicon photomultiplier (SiPM) array for readout. Purpose In aerospace engineering design of GRD, there are many key points to be studied. In this paper, we present the specific design scheme of GRD, the assembly and the performance test results of detectors. Methods Based on Monte Carlo simulation and experimental test results, the specific schematic design and assembling process of GRD were optimized. After being fully assembled, the GRDs were conducted performance tests by using radioactive source and also conducted random vibration tests. Result and conclusionThe test results show that all satellite-borne GRDs have energy resolution <16% at 59.5 keV, meeting requirements of satellite in scientific performance. The random vibration test shows that GRD can maintain in a stable performance, which meets the requirement of spatial application.