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In order to obtain the overlying strata structure and the stress transfer law of floor under the influence of section coal pillar after the upper protective layer is fully mined, the rational arch axis equation is deduced based on the three-hinged inclined arch theory. The stress distribution of coal pillar floor with different widths is simulated numerically. Based on two methods of three-hinged inclined arch and elastic mechanics theory, the analytic solution of stress distribution of bottom plate of protective layer is obtained and verified by field measurement. The results show that the shape parameters of three-hinged inclined arch are dynamically correlated with the width of retained coal pillar, the mining height of coal seam and the pressure relief width of goaf. When the width of coal pillar is larger than 15 m, the additional stress caused by three-hinged inclined arch structure will occur in the re-compacted area of goaf floor, and the extreme stress point will move to the center of goaf with the increase of coal pillar width. The field test shows that the stoping roadway of protected layer should be arranged in the wrong way, and the reasonable wrong distance is 10-20 m.