To effectively dissolve the calcium carbonate crystal in the tunnel drainage blind pipe, and to explore the key factors of the cleaning effect of the drainage pipe crystal, a composite environmental protection cleaning agent is selected and studied. Three different crystal dissolution experiments are conducted in the laboratory environment including the initial saturated cleaning agent solution dissolution test, continuous saturated detergent solution dissolution test, and initial saturated detergent solution circulation dissolution test. The laboratory experimental results show the following: (1) The dissolution efficiency of the detergent solution is the highest at the initial stage of the reaction. When the pH value of the solution rises to 4, the dissolution rate begins to decrease. (2) The dissolution rate of stalactite is about 0.7 g/h per 100 mL of continuous saturated detergent solution. The agent is applied to an engineering case, and the applicable results show that the high pressure cleaning and circulation cleaning process can achieve ideal cleaning effect.