Abstract: In the paper designed four complex detectors and observed their background counting rates in balloon space environment. The primary crystal is Nal(Tl) scintillator of each complex detector. Its veto crystal is BaF₂, BGO, CsI(Tl) and Nal (Tl) separately. The results shown that the integral background counting rates of four complex detectors in region of energy 30~350keV at altitu-de31~36km are near. There is no obvious difference each other on y background noise level in space environment. The differential counting rates of Nal/BGO and NaI/BaF₂ detectors are lower than Nal/CsI and Nal/Nal detectors.