A model of collisional quantum interference was derived in an atom-diatom system [Chem. Phys. Lett. 339 (2001) 413]. In this Letter, a theoretical model of CQI is derived in a polar diatom-diatom system, based on the first order Born approximation of time dependent perturbation theory and taken into account of the multipolar interaction potential. The key factors in the determination of the differential and integral interference angles are obtained. CO A(1)Pi(nu = 0)-e(3)Sigma(-)(nu = 1) system in collision with HCl is calculated. The changing tendency of the interference angles with the experimental temperatures is obtained. (C) 2002 Elsevier Science B.V. All rights reserved.