背景导向纹影(BOS)因其测试方法简单、测试区域宽、对流场无影响等特点，在超声速流场密度场的测量中有很好的应用前景。根据相关原理，搭建了BOS测试平台并对设计出口Ma=1.9处于严重过膨胀下的喷管出口密度场进行了测量。对实验获得的图像进行处理，获得了喷管出口区域内完整的定量密度场。运用计算流体力学对相同实验状态下喷管出口流场进行了精细的数值模拟。将其与实验结果进行了对比分析，发现实验结果与数值模拟所得的波系结构及激波强度都能够很好地吻合，特别在射流边界外的密度误差在1%以内。这证明了BOS技术能够在有复杂波系的超声速流场密度场测量中获得良好的结果，为超声速流场密度从传统的定性测量转变到定量测量提供了可靠的测试方法。

Background Oriented Schlieren (BOS) has good application foreground because of its conceptual simplicity，large measurement region，non-intrusive measurement and so on. Based on the principles，a BOS system is set up and the density of Ma=1.9 nozzle under over-expanded condition has been measured by BOS. By processing the experimental images，the quantitative density information of the supersonic jet can be obtained. Then the flow is numerically simulated by Computational Fluid Dynamics (CFD). The experimental results agreed well with the data from CFD，especially the deviation of the density in the outside region of the jet flow is less than 1%. It can be concluded that BOS can be applied in the applications of supersonic flow and offer a reliable method to measure the density in a quantitative manner.