The purpose of the study is to determine grid cell of radar relationship, and to promote the radar data on hydrology field. The study region is the Chungjudam basin with a drainage area of $6,648km^{2}$ located within the 260 km circle under the DWSR-88C C-band umbrella(Kwanak Mt Radar). Grid cell was produced to extract radar reflectivity and rainfall data of the same time and point using Arc-view software package. The grid cell size is to estimate mean correlation coefficient for $1km{ imes}1km,;2km{ imes}2km,;3km{ imes}3km$ grid. The result of mean correlation coefficient showed good result(0.57) for the $1km{ imes}1km$ grid cell. The 32 rainfall stations Z-R relationship was estimated in Chungjudam basin.