Ultra-low density foam cement slurry is an effective technical measure to solve cementing leakage and improve cementing quality for low leakage pressure well. In addition to the foam cementing slurry development and the performance optimization, confirming static liquid column pressure (SLCP) at different annulus depth is necessary for foam cementing slurry application. With the help of real gas state equation, taking the influence on N2 filling volume by the variation of temperature and pressure into account, a mathematical model of SLCP and density of foam cement slurry together with the well depth was established, the implicit function is solved by iterative method and the program operation is realized by using VB language. The influence rules of gas content variation and well depth on foam cementing slurry density and SLCP are analyzed; the cementing slurry column structure design ideas for foam cement slurry are given for cementing leakage prevention and pressure stability which can be reference and theoretical basis for balanced pressure cementing design. This design method has been proved to be reliable by field application.