Abstract: Abstract: Water hyacinth is one of the most fertile plants in the world and is considered to be one of the most difficult aquatic plants to control because of its strong reproductive ability and easy diffusion. As the moisture content of water hyacinth plant is up to 95%, the dewatering of water hyacinth becomes the key technical link to realize its subsequent resource and harmless utilization, and the degree of dehydration becomes the bottleneck restricting its subsequent treatment. In the previous work, the influence factors such as dehydration mode of water hyacinth, nutrient loss rule of spiral solid-liquid separation and different degree of comminution are studied. At the same time, the pilot-scale pretreatment scheme of water hyacinth in large-scale treatment is compared, but research on the technical parameters of water hyacinth dehydration in large-scale treatment is limited. In order to obtain the technical parameters of large-scale treatment and disposal of water hyacinth with low cost and high efficiency, this study was based on the working condition of 50 t/d processing ability, based on the SHJ- 400 water hyacinth solid-liquid separator and horizontal cutter shaker developed independently. The effects of crushing size, feed amount and extrusion dewatering residence time on the large-scale dehydration effect of water hyacinth were studied by single factor test, and the distribution of dry matter, nitrogen, phosphorus and potassium nutrients in dewatering residue and extruded juice were obtained at the same time. The results showed that the suitable solid-liquid separation technical parameters of water hyacinth were obtained, that was, the suitable comminution diameter of water hyacinth was 20 - 30 mm, the feed quantity was 8 t / h, and the retention time of extrusion and dehydration was 3 min. The percentage of dry matter in dewatered residue and extruded juice of hyacinth was 61.67% - 65.48% and 34.52%-38.33%, respectively, while most nitrogen, phosphorus and potassium nutrients remained in extruded juice. The capacity reduction rates of water hyacinth crushing and solid-liquid separation were 50.25% and 93.70%, respectively. In addition, taking the treatment capacity 50 t/d demonstration project as the test platform, the operating effect parameters of the dehydration operation under the actual operation condition were obtained, that was, under the condition of the initial moisture content of the water hyacinth 95.08%, after solid-liquid separation, the moisture content of dewatered residue of water hyacinth was 83.21%, the dewatering rate was 78.59%, and the treatment capacity of water hyacinth solid-liquid separator was 6.25 t / h. The cost of solid-liquid separation of water hyacinth was 4.40 yuan/t. We obtained low cost and high efficiency water hyacinth large-scale treatment dewatering operation technical scheme, and provided the technical support for forming the whole solution of the water hyacinth large-scale treatment and disposal project.