The paper analyzes the applicability of Weibull Density Distribution and Kernel Density Estimation in research of scientific productivity and collaboration group size. The datasets from five categories were retrieved and downloaded from ISI, and they are used to verify Kernel Density Estimation curve fits well with the Weibull Density Distribution curve. As a comparatively convenient function, Kernel Density Estimation can be used as a model to study the relationship between scientific productivity and group size. The best group size and reasonable group size are suggested through Kernel Density Estimation model. We assumed that the best group size in scientific cooperation is positive to discipline biology connotation, however, the result didn’t show such correlation obviously.