The invention provides a geometrical characteristic and dilution rate modeling method for a cladding layer in laser additive remanufacturing, and relates to the technical field of laser additive remanufacturing. The method comprises the steps of firstly, carrying out a single-cladding pass single-factor experiment to obtain a process parameter optimization range and model verification data; secondly, performing a single-cladding pass orthogonal experiment to obtain a relatively excellent parameter combination and model building data; thirdly, obtaining a cross section test sample of the cladding layer by cutting a test piece, measuring the geometric size of the cross section of the cladding layer, and calculating a dilution rate; and finally, establishing an interactive linear regression relation equation of a geometric characteristic and the dilution rate of the cladding layer, solving a relation coefficient through a BreedPSO algorithm, and verifying the fitting and prediction precision of a model. According to the geometrical characteristic and dilution rate modeling method for the cladding layer in the laser additive remanufacturing, provided by the invention, the technical problem of low fitting precision between the forming size of the geometric characteristic and the process parameters of single cladding pass in the laser additive remanufacturing is accurately solved; the modeling method is simple and high in accuracy; and the production cost can be reduced.