Making use of the Bogoliubov-de Gennes equation, we study quasi-particle spectrum and the vortex core structure of a single vortex in quasi 2Ds-wave superconductors for smallpF&xgr;0,wherepFis the Fermi momentum and&xgr;0is the coherence length. During our numerical calculation the electron number is conserved for eachpF&xgr;0.We find that the number of bound states decreases rapidly for decreasingpF&xgr;0.Also we find that the core structure, the current density distribution and the local density of states strongly depend on the value ofpF&xgr;0due to the number and the peak positions of bound states. ©1999 American Institute of Physics.