The flowfield structure and their aerodynamiccharacteristics over an ogive cylinder were studied by means offlow visualization and surface pressure measurement in a watertunnel and a wind tunnel. The existence of multi asymmetricvortices over long slender bodies was experimentally con-firmed at large angles of attack and in the subcritical Reynoldsnumber range. The spatial 3 -D characteristics of the multivortices system were analyzed and a physical model was devel-oped. The topological structure of different patts in crossflow plane was studied and the mechanism goving the for-mation of asymmetric vortices and multi-vortices was dis-cussed from the viewpoint of stability of the topological struc-ture. It was concluded that the maximum in the sectional sideforce distribution curve are not caused by the shedding ofhigher position vortex, but by the cross-over to the symmetricplane of the lower-position vortex.