The invention discloses a method for determining a tectonic soft coal firmness coefficient. The method comprises the following steps: selecting tectonic soft coal, recording a burial depth of the tectonic soft coal, determining a firmness coefficient f1 according to a national standard coal firmness coefficient determination method (GB/T23561.12-2010), compacting the tectonic soft coal to shaped coal according to different pressures of the burial depth of a coal seam, wherein dwell time is t, then determining uniaxial compressive strength of a briquette coal, calculating a firmness coefficientf2 of the briquette coal, if f1 equals to f2, the dwell time is t0, if f1 does not equal to f2, the dwell time t is increased or decreased, repeating the above steps until f1 equals to f2 so that thedwell time is t0, finally determining the firmness coefficient of a coal body with other burial depth in a same mining area, compacting the tectonic soft coal to the shaped coal, wherein the pressureis obtained by calculating the burial depth, the dwell time is t0, determining the uniaxial compressive strength of the briquette coal, and reckoning the firmness coefficient of the tectonic soft coal according to a relation of the firmness coefficient and the uniaxial compressive strength. The method is simple and convenient, and a measuring result accords with practical situation.