A prompt gamma neutron activation analysis setup was developed for heavy metal detection in aqueous solutions with a $$300\,\hbox {mCi}\,\,{}^{241}$$ 300 mCi 241 Am-Be neutron source and a $$4\times 4$$ 4 × 4 inch (diameter $$\times $$ × height) BGO detector. In the present work, heavy metals, including Mn, Cu, Ni, Cr and Zn, were measured by the setup. The minimum detectable concentrations of Mn, Cu, Ni, Cr and Zn were 246.6, 391.2, 218.1, 301.5 and 2804.1 ppm, respectively. The minimum detectable concentration of each element and the linearity response between the characteristic peak counts and elements concentrations have been studied. And the results showed that all heavy metals had a good linear relationship between characteristic peak counts and concentrations.