The mechanism of homogeneous acidic catalytic conversion of CH2Cl2 to CHCl3 and CCl4 and simultaneously to CH3Cl and CH4 in solutions of the H(CHB11Cl11) superacid in dichloromethane was identified. The role of the catalysts is played by the chloronium cations formed in the solutions. The processes proceed through the exchange of the Cl atoms of the CH2Clgroup of cations CH2Cl-Cl+-CH2Cl and CH2Cl-Cl+-CH3 for the H atoms of the CH2Cl2 molecules, transforming them initially to CHCl3 and then to CCl4. Simultaneously, the CH3-group of cations CH3-Cl+-CH2Cl and CH3-Cl+-CH3 exchanges its H atom for the Cl atom of CH2Cl2 molecules, transforming them to CH3Cl and further to CH4. The processes of chlorination and dechlorination lead to cyclic reproduction of chloronium cations.