The invention discloses a method for detecting underwater sound field information, a device for detecting underwater sound field information and an underwater acoustic sensor. The method includes the following steps that: 1) a light source of which the spectral width is larger than 25nm and of which the light intensity is above 1mW is selected, and light emitted by the light source is processed, so that Gaussian light can be obtained; 2) the Gaussian light passes through a first polarizer, and beam splitting processing is performed on the Gaussian light, so that a horizontally polarized light component and a vertically polarized light component can be obtained, and one of the horizontally polarized light component and the vertically polarized light component is received by a detection arm optical fiber, and the other light component is received by a reference arm optical fiber; 3) a light component reflected by the interior of the detection arm optical fiber and a light component reflected by the interior of the reference arm optical fiber are coupled, and obtained coupled light passes through a second polarizer, and then is emitted out; and 4) the spectral center wavelength change of the emergent light before and after the probe of the detection arm optical fiber detects acoustic waves in water is recorded by a spectrograph; and 5) and the magnitude of the sound pressure of an underwater sound field is calculated according to the spectral center wavelength change. The method, device and the underwater acoustic sensor of the invention have high detection sensitivity and can measure weak sound fields.