It is very important and instructive for us to further investigate the formation mechanism of hot spots in explosive initiation in wide pressure zone. Magnetically driven quasi-isentropic compression (shock less compression) is an effective method to research the dynamic behaviors of un-reacted explosives in high pressure. Based on the working principle of electro-magnetic force produced by large current,the shockless compression technique driven by magnetic force is first achieved in domestic. A pressure of 5 GPa is obtained in the experiments of magnetically driven quasi-isentropic compression. The particle velocities of the interface between JO-9159 explosive and LiF windows are gained. The isentropic compression procedure was numerically simulated by one dimensional hydrodynamics code. The simulated particle velocities are in good agreement with experimental results. The gradient of particle velocities between the windows and the samples becomes larger when samples become thicker. The strain ratios of the samples are in 10⁵/s~10⁶/s, and the peak of strain ratio becomes narrower but higher when samples become thicker.