At present the foundation pit supporting pile soil pressure calculation mostly applies the classical earth pressure theory or normative experience method, which deduced under the limit equilibrium state, and is significantly different from the foundation pit engineering under non-limit state of soil. Based on the previous research results, applies the method of level-layer analysis and combining with the reasonable assumption to deduce the calculation formula of quasi active earth pressure of non-limit state between initial state and limit state, and improves the method of level-layer analysis. Through the analysis of the foundation pit engineering examples, it shows that the obtained quasi active earth pressure value is basically consistent with the actual measured earth pressure, and the caculating result of the method of level-layer analysis relatively larger than the consequence of Rankine active earth pressure, but it is less than the static earth pressure value, which in line with the non-limit state law of earth pressure. It also illustrated reasonableness of the previous assumptions and correctness of quasi- active earth pressure formula.