The invention relates to a functional filling material auxiliary agent used for papermaking field. The filling material auxiliary agent comprises the following raw materials by weight fraction: 100 parts of diatomite original soil, 5 parts of wollastonite powder, 5 parts of heavy calcium, 0.55 parts of cation polyacrylamide, and 33.2 parts of a diatomite composite flocculating agent (the patent application number: 201410769722.3). The functional filling material auxiliary agent has eight functions of increasing pulp saving rate, prolonging felt and screen cloth life, alleviating sewage processing burden, increasing output, increasing the physical indexes (ring crush compression resistance, tension intensity, surface fineness and color) of the paper, saving energy, saving drying steam amount, and aiding retention and drainage, and has high cost performance.