Abstract: To obtain the propagation laws and classification of pillar abutment pressure in floor, with the help of UDEC software, the paper stimulated 7 kinds of the propagation form, distribution and variation trend of pressure concentration coefficient in floor. Based on these, it carried on nonlinear regression analysis of coal pillar's width and propagation depth, the results of the study had shown that pillar pressure propagation depth was in exponential relationship with coal pillar width, and the pressure propagation direction coincided with the direction of gravity, which presented the semi-elliptical base distribution. The stress distribution of coal pillar floor changed with different sizes of pillar, when the pillar width was larger, the stress was higher on two ends than on middle of pillar, and the result were contrary when it's smaller, and stress was symmetrical distribution centering on pillar axis.