The deflagration-to-detonation transition (DDT)process of high-energy propellant was experimentally investigated and the velocity of flame, predetonation column length(PCL), detonation velocity and pressure were obtained. It is found that in a certain density(φ)range,the PCL-φ is a U-shaped curve and the detonation velocity linearly increases with the density. The experimental results are theoretically analyzed.