The innovation of the current work is to quantify the influence of the uncertain inflow conditions in altitude test facilities. Uncertain inflow condition data is from a real test from an altitude simulated test facility at 100% corrected rotating speed. The sample space is 1000 to meet the requirement of hypothesis testing. The Kolmogorov-Smirnov test is introduced to confirm the statistical characteristics of inflow uncertainties. Non-intrusive polynomial chaos expansion (NIPC) is introduced to quantify the inlet uncertainty on NASA Rotor 37. The sensitivity analysis (SA) quantified the importance of these two parameters to the aerodynamic performance. Three typical operating conditions, choke, peak efficiency, and near stall are compared and discussed. The results showed that near stall condition is the most sensitive to uncertainties. The relative standard variation of mass flow rate is approximately 0.084%, which is much higher than that of the uncertain inflow total pressure and total temperature. The reduction of integrated surge margin is about 1.25%. The sensitivity rank of aerodynamic performance parameters is mass flow rate > isentropic efficiency > the total pressure ratio.