To study the characteristics and laws of jet formation process of circular shaped charge of cutting inward, the tri-dimensional numerical simulation of shaped charge was done by ANSYS/LS-DYNA program. The jet formation photographs, jet velocity gradient distribution curve and time history curve of maximum jet velocity of typical moment(4, 10, 22, 25, 26, 44 μs)under different detonation form were obtained. Results show that detonation point number and its synchronicity have great influence on jet formation performance of circular shaped charge. When detonation forms are two points, four points and eight points symmetry synchronous initiation of the whole round, jet shape are "inside the runway and outside the oval", "both inside and outside the approximate square", and "inside the wheels and outside the approximate octagon ". respectively. The jet formation performance with the increase of detonation point number is gradually getting better, and finally close to the circular. When detonation form is two points, four points and eight points symmetry synchronous initiation of the whole round, the jet velocity variation law with time in the cross-sectional area is almost the same, and the moment of jet maximum velocity is 10 μs. Secondary collision phenomenon of jet head happens at the circular symmetric axis. This alters significantly the direction of the newly formed jet, and made the motion of the newly formed jet along with the direction of axis of the circle. The moment of secondary collision of jet is different with the difference of detonation form. The moment of secondary collision of jet advances gradually from 43 μs to 36 μs with the increase of detonation point number.