The acoustic target strength (TS) of an underwater platform is usually tested in shallow water. Utilizing normal mode theory, the analytical formula of the TS of an underwater object in shal-low water is derived, based on the average-measurement method, and its physical significance is an-alyzed deeply. Analysis shows that, as for as a certain azimuth, TS is dependent on the target scat-tering function values at a few vertical incident angles, Ɵm, and scattering angles, Ɵn. Ɵm and Ɵn are discrete, their values depending on normal-mode order, m, n. Furthermore, TS is concerned with both the marine environment and the testing range, and it is approximately equal to the free-field target strength, TS free , when the testing range is large enough. A new TS measurement method put forward, namely Modal-Filtering Measurement (MFM), based on a vertical source array and a verti-cal hydrophone array. According to theoretical analysis, MFM method performs well in both interface reverberation resistance and testing efficiency, compared with the average-measurement method and the classical vertical array method, its result is closer to TSfree.%水下运动平台的声目标强度测量试验多在浅海环境中进行。文章根据简正波理论推导了基于平均测量法的浅海环境中水下物体声目标强度TS的解析表达式，深入分析了TS的物理意义。分析表明，在确定的方位角上，TS与分布在一定范围内的垂直入射角兹i和散射角兹s所对应的目标散射函数值有关，兹i和兹s是离散的，其取值取决于简正波阶数；同时，TS还跟海洋环境和测试距离有关，当测试距离非常大时，约等于自由场声目标强度TSfree。文中还提出了一种基于垂直发射阵和垂直接收阵的声目标强度测量方法，即模式滤波测量法（Modal-Filtering Measurement，MFM）。理论分析表明，MFM法具有很好的抗界面混响性能，并且跟平均测量法和垂直阵常规测量法相比，具有更高的测试效率，测试结果更接近自由场声目标强度。
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