Standard sieves were used to grade the catharanthus roseus cell aggregate rates of the previous ten subcultures. From the experimental results of the mean diameter of the catharanthus roseus cell aggregates in sub-cultures

it was found that the size decreased first

then increased and finally reached a relatively stable value. A trial is presented here to apply fuzzy sub-cluster theory to the high degree dispersion size distribution of plant cell aggregates. A model equation of integrate size distribution of plant cell aggregates was obtained. The model parameters were estimated by Marquardt nonlinear optimal method. The model values agreed well with experimental data.