傅里叶变换离子回旋共振质谱法也称作傅里叶变换质谱分析，这是一种根据给定磁场中的离子回旋频率来测量离子质荷比（m/z）的质谱分析方法。

彭宁离子阱（Penning Trap）中的离子被垂直于磁场的震荡电场激发出一个更大的回旋半径，这种激发作用同时也会导致离子的同相移动（形成离子束）。当回旋的离子束接近一对捕集板时，捕集板上会检测到影像电流信号。这种信号被称为自由感应衰减（FDI），是一种由许多重叠的正弦波组成的瞬态或干涉图。通过傅里叶变换，我们可以从这些信号数据中萃取出有用的信号形成质谱。

傅里叶变换离子回旋共振质谱法（FTICR-MS）具有非常高的析像能力，可以十分精确地测定物质。因此对于FTICR-MS的使用主要是利用它的高分辨率检测分子组成。这一检测的理论前提是元素在这一过程中会发生质量亏损。 此外，FTICR-MS通常也被用来研究复杂的混合物。这是由于它所产生的分析图像具有较窄的峰宽，能够将两个质量相近的离子返回的信号（质荷比m/z）区分开来。

Fourier transform ion cyclotron resonance mass spectrometry is a type of mass analyzer (or mass spectrometer) for determining the mass-to-charge ratio (m/z) of ions based on the cyclotron frequency of the ions in a fixed magnetic field. The ions are trapped in a Penning trap (a magnetic field with electric trapping plates) where they are excited (at their resonant cyclotron frequencies) to a larger cyclotron radius by an oscillating electric field orthogonal to the magnetic field. After the excitation field is removed, the ions are rotating at their cyclotron frequency in phase (as a "packet" of ions). These ions induce a charge (detected as an image current) on a pair of electrodes as the packets of ions pass close to them. The resulting signal is called a free induction decay (FID), transient or interferogram that consists of a superposition of sine waves. The useful signal is extracted from this data by performing a Fourier transform to give a mass spectrum.