The photodissociation of chlorobromomethane (CH2BrCl) has been studied using unrestricted Hartree-Fock (UHF), configuration-interaction-singles (CIS), and complete active space self-consistent field (CASSCF) levels. The result of oscillator strengths indicate that the photochemistry reactions of CH2BrCl are processes where the n(Br)→σ*(C-Br) transition are excited to repulsive states leading to direct carbon-bromine bond breaking reactions. And the 1A’ →1A’ state is the important transition in photolysis of chlorobromomethane.