Abstract: This paper is the first part of characteristic wave of transversal disturbance at baroclinic shear basic flow. The distribution of spectrum point is studied. The results show that, when the wind shear of basic flow is not zero, there exists continuous spectrum of gravitational inertial wave and vortex wave. Under usual circumstances, to synoptic scale, the continuous spectrum area of this three waves (that is distinct separated) are not overlap. When the disturbance scale is smaller than the critical scale lo, there exists a overlap of the continuous spectrum area of two waves (vortex wave and a gravitational inertial wave),and when it is smaller than l0/2, there exists a overlap of the continuous spectrum area of three wave (vortex wave and both gravitational inertial waves).This two kind of waves can not be separated at this moment, if the disturbance is instable, the real part of this frequency is in the overlap spectrum area while there appears overlap spectrum.