A mass spectrometric analyzer and an analysis method based on the detection of ion image current are provided. The method in one embodiment includes using electrostatic reflectors or electrostatic deflectors to enable pulsed ions to move periodically for multiple times in the analyzer, forming time focusing in a portion of the ion flight region thereof, and forming an confined ion beam in space; enabling the ion beam to pass through multiple tubular image current detectors arranged in series along an axial direction of the ion beam periodically, using a low-noise electronic amplification device to detect image currents picked up by the multiple tubular detectors differentially, and using a data conversion method, such as a least square regression, to acquire a mass spectrum.