Abstract: Experiments are done meticulously in laboratory for determining the possibili-ty of application of BGO crystal in coal nuclear well logging. The light outputof BGO is enhanced by choosing surface treatment and better photomultiplier.Data of nature and scattered gamma rays are obtained using BGO crystal underthe condition arranged as nearly as possible to that of field and are comparedwith that obtained by using NaI (Tl). The dependence of light output of BGOcrystal with temperature is measured. Some means are used to compensate thecount losses resulted from the variation of temperature. A nuclear logging toolwith BGO crystals, for coal logging, is finished.