Abstract: In this paper,a cartographic projection system in variable scale suitable for city tourist maps is put forward,The principle is that the mathematical basis for variable scale maps is established by an inverse projection(A) from a conventional city plan on an auxiliary sphere(AS) and then by a projection other than(A) from AS onto a new plane.The combination of various projections will play a role which satisfies the properties of different city structures,which ensures to the system certain flexibility.The size of the auxiliary sphere and the transformation formulas between azimuthal projections have been discussed as well.An experiment of the variable scale map of Beijing is calculated and the sketch shows the design is successful.