The influencing rule was studied in small diameter charge detonation velocity on different condition, thus the experiential relational expressions of x booster explosive were obtained in constraint condition of 45^# steel or PMMA. The results indicate that the bigger charge diameter is, or the bigger constraint resistance is, the greater small diameter charge detonation velocity is. With increasing charge diameter, the effect of charge dimension and constraint condition exerted on was less, and vice versa. For a specified charge density, the detonation velocity can be controlled by adjusting charge dimension and constraint condition to meet different needs.