An analysis of literary sources showed the absence of multifactorial regression dependencies of the density of waste briquettes of plant origin on such parameters of the briquetting process with a hydraulic press as pressure and temperature, which determined the subject of this study. The article defines adequate multifactor power regression dependences of the density of waste briquettes of plant origin on the parameters of the briquetting process by a hydraulic press, which can be used in the development of a methodology for engineering calculations of the parameters of a hydraulic press for briquetting waste of plant origin. Among the waste of plant origin, the following were considered: pile of flax, sunflower husk and sawdust, and the parameters of the briquetting process studied include briquetting pressure and temperature. In processing the results of preliminary single-factor search experiments, the regression analysis method was used. The adequacy of the regression models was estimated using the Fisher criterion. The multiple correlation coefficients obtained for the constructed regression models showed high accuracy of the results at the level of 0.9830 … 0.9935. According to the Student criterion, it was determined that among the studied factors of influence on the density of briquettes of plant origin waste, the briquetting pressure affects the density, and the briquetting temperature has the least effect. Response surfaces and two-dimensional sections illustrate the relationship between plant waste briquette density and process parameters. The obtained regression dependences of the density of plant waste briquettes on the parameters of the briquetting process using a hydraulic press will contribute to an increase in the prevalence of the use of biomass briquettes in the energy sector of the economy, as well as potential savings of natural resources.