Abstract: In order to solve the problem of coal face direct passing collapse column, hydrochloric acid softening method of coal face direct passing collapse column is proposed and carried out successfully. Through the methods of laboratory immersion test, rock mechanical characteristics test, X-ray diffraction and so on, the change law of rock sample in different concentrations hydrochloric acid, soaking time and its softening mechanism are studied. The study results show as follows: 1) The mechanical strength of sandy mudstone is negative logarithmic law changes with soak time of hydrochloric acid solution; 2) The exponential law of the mechanical strength of sandy mudstone decreases with hydrochloric acid solution concentration increasing; 3) With hydrochloric acid solution concentration increasing, its porosity increase, yield point is obvious and plastic to raise, but its elastic modulus changes insignificantly; 4) The decrease in the contents of muscovite and kaolinite mainly lead to the decreased mechanical strength of sandy mudstone; 5) Suitable hydrochloric acid solution concentration, soak time, the amount of injecting liquid and the cutting depth of the shearer can make sure of coal face’s normal advancement. Practical application shows that this safe, reliable, efficient method can provide references for coal face direct passing collapse column under similar conditions.