In this paper we use a series of local quasi-two-dimensional Cartesian coordinates to study the impact of vertical wind shear on spiral wave instability in tropical cyclones, and calculate the distribution of the growth rate of spiral wave instability on the spiral line. The conclusions are as follows: at the beginning, the growth rate of instability increases as the tropical cyclone radius extends, and became the largest on the maximum wind-speed circle; then it decreases later and goes up again when it gets a local extreme value. That is to say, there are two maximums on the spiral line; this is in accordance with the actual situation of tropical cyclones. The growth rate of spiral wave instability is closely related to the vertical shear of the basic flow and stratification parameter. The greater the vertical shear is, or the smaller the stratification parameter is, the greater the growth rate is; that is to say, the smaller the number of Richardson is, the greater the growth rate of instability is.