The invention provides an automatic processing method of seabed sediment particle size analysis data; an optical platform, a sample dispersion device and a computer data processing module are adopted; the optical platform includes a light source, a lens and a detector; the sample dispersion device includes a container, an ultrasonic probe and a centrifugal pump; the computer data processing module is connected with the detector through a signal transmission module; an inspection report generation unit is used for outputting information of a particle size-content calculation unit, a parameter calculation unit and the user computer data processing module to a report. The automatic processing method greatly increases the application level of a laser particle size analyzer in the field of ocean engineering detection, not only improves the working efficiency, but also improves the accuracy of the data, avoids error generation during artificial abstracting of the data, and provides more accurate basis for judgment of a seabed sedimentary environment and prediction of engineering construction stability.