Potential energy surfaces of the HClCO dissociation to H+ClCO and Cl+HCO in the lowest three electronic states (S-0, S-1, and T-1) have been investigated with ab initio molecular orbital method at the levels of the complete active space self-consistent-field, single- and multi-reference MP2. The results show that the C-Cl bond cleavage on the S-1 surface is the most probable mechanism for the HClCO photodissociation at 230-320 nm. In comparison with formyl fluoride (HFCO), a significant difference was found in photodissociation dynamics between HClCO and HFCO, and this has been discussed in detail.