This study explored the reaction characteristics and the burning properties of low-toxicity B/CuO delay compositions. Firstly, differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to measure and analyze the reaction characteristics. Afterward the delay compositions of different formulas were processed to be cylindrical pellets and were characterized by measuring their burning properties including igniting ability, burning rate and output flame temperature. At last, the influence of each ingredient of the formula on the reaction characteristics and the burning properties were analyzed from the experimental data. The results showed that the thermal onset temperature of B/CuO mixture was significantly lower than that of B powder. The thermochemical characteristics of B powder could be improved by adding CuO powder. The B/CuO delay compositions were possessed of lower ignition energy, higher output flame temperature, and greater adjustability in burning rate. Furthermore, B powder only had low toxicity and CuO powder was generally regarded as being less toxic. The B/CuO system was suitable as an low-toxicity delay composition.