The technique of soil nailing has already got an extensive application to deep foundation pit engineering

but the research of its work mechanism and the calculation method is still not perfect. Now the numerical simulation experiments are prevalent; but it must to do a large numbers of triaxial or true triaxial tests to gain the exact model and other parameters for local soil. So a simple calculation model is founded based on three supposes

the writer also studies on the work mechanism of soil nailing and finds the regulation that Curve of nail stress is “Two half parabola”

and the concerned formulas is deduced. Combining the Pengcheng underground square engineering

the data of displacement for pit are measured. The stresses of soil nailing are also measured; these data verifies the accuracy of the formulas. The analytical algorithm is worth for reference in the similar case.