This study was carried out to investigate the change of average .specific resistance according to suspension concentration for study phenomena occurring during filtration period. As the results of this study, the following conclusions were obtained. The average specific resistance in 1% $CaCO_3$ suspension was showed power function(R=0.99), whereas in TOYO 5C and TOYO 5A paper were made little difference under high pressure. It represented from results that filtration theory in concord with cake filtration was no affected the average specific resistance of filter medium in cake filtration. In case of 0.1% $CaCO_3$ suspension filtration, the TOYO 5C was showed power function, whereas in TOYO 5A paper differently. In the present study, the $P_1$ value was calculated from the average specific resistance by filtration method. Therefore, $P_1$ value were $1.68 imes 10^4Pa$, $4.05 imes 10^3Pa$, and $3.15 imes 10^3Pa$ in $5.3 imes 10^4Pa$, $1.3 imes 10^4Pa$, and $8.2 imes 10^3Pa$, respectively. We concluded that propriety of new filtration theory was also proved.