The closed bomb test system was used to investigate the burning rate of B/KNO₃. Results show that the linear burning rate increases as the pellet density decreases, and the product formation rate of B/KNO₃, which affects pressure-time curves, is significantly affected by the pellet size. Additionally, the linear burning rate B/KNO₃ is not consistent with single exponent equation, and can be expressed with step-wise function. Below 7 MPa, the linear burning rate is proportional to pressure. But as pressure higher than 7 MPa and lower than 50 MPa, the linear burning rate does not change with pressure.