前驱波是一种暂态信号，是在震源成核过程中发射出的低频波，可能是一种有价值的短临前兆信息。本文选取功率谱、傅里叶谱和边际谱分析方法，对黑龙江及邻区3次中强地震前，水位和竖直摆倾斜共5次低频前驱波异常进行分析，给出水位和竖直摆倾斜低频前驱波频谱特征，丰富了频谱分析方法在黑龙江及邻区前兆信息提取中的应用。

 The precursory wave is a kind of transient signals and low-frequency waves in the process of source nucleation, maybe it is an important prediction value and reliable short-impending precursor information. This paper extracted water level and vertical pendulum tilt respectively 5 times low-frequency precursory wave anomalies before 3 times moderately strong earthquakes in Heilongjiang and adjacent area by selecting the marginal spectrum method based on Hilbert Huang transform, and gave the spectrum characteristics of low-frequency precursor wave of water level and vertical pendulum tilt, that have enriched the three methods’ application of extracting precursor informations in Heilongjiang and adjacent area.