The law of the burning rates of B/CuO delay compositions at ambient temperature from -50 ℃ to 70 ℃,and with the boron contents increasing from 8.3% to 20% were studied. Results show that when the boron content is 8.3%, the B/CuO delay compositions are misfired, and the burning rates increase with increasing of boron contents from 11% to 20%. When the boron contents are from 14% to 18%, the burning rates almost keep the same value. With the increasing of ambient temperature, the burning rate also has a little increase. Least square method was used to simulate the burning rates, and a burning rate formulation of B/CuO delay compositions was put forward.