The differential quadrature method (DQM) is used to discretize aeroelastic flutter equations of the truncated conical shells. With the first-order piston theory of aerodynamic force, the critical flutter pressure is obtained by eigenvalue analysis. The parameters, semi-cone angle, radius-thickness ratio, length-radius ratio, are emphasized on the influence to critical flutter pressure. The results show that DQM has good accuracy and calculating efficiency. The circumferential wave numbers with the smallest critical pressures of 1-2 coupled flutter are different with geometric parameters. The critical flutter pressure decreases as semi-cone angle increases, rises as radius-thickness ratio increases, and decreases as length-radius ratio increases.