Gene sequencing method and gene sequencer

An embodiment of the invention provides a gene sequencing method and a gene sequencer, and relates to the technical field of gene sequencing. The gene sequencer comprises an excitation light path used for conducting an excitation light beam generated by an excitation light source to a fluid chip with a flow channel, wherein a sample to be tested flows through the flow channel; an imaging light path which is used for collecting fluorescent light generated by the object to be detected through excitation of the excitation light beam and imaging the fluorescent light on an imaging camera arranged on the imaging light path; and a focusing light path used for transmitting a focusing light beam generated by the focusing light source to the fluid chip; and objective lenses are arranged on the excitation light path, the imaging light path and the focusing light path, the objective lenses are located above the fluid chip and can move to change the distance between the objective lenses and the fluid chip, and the focusi