The utility model relates to an improved online switching system for producing singlet and/or doublet polyethylene by adopting a slurry process. The improved online switching system for producing the singlet and/or doublet polyethylene by adopting the slurry process is characterized in that a material discharged by a first reactor enters into a second reactor for continuous reaction via an automatic switching valve newly additionally arranged on a first pipeline and the original manually operated valve by virtue of the original manually operated main valve, then enters into a third reactor to realize series operation and then enters into the next working procedure from the third reactor for solvent separation and product purification, so that a doublet or singlet wide molecular weight distribution polyethylene product is obtained; the material discharged by the first reactor enters into the third reactor via the original manually operated valve by virtue of an automatic switching valve newly additionally arranged on a second pipeline to realize parallel switching operation and enters into the next working procedure from the third reactor for solvent separation and product purification, so that a singlet narrow molecular weight polyethylene product is obtained; a newly additionally arranged hexane flushing pipeline and a related valve are connected on each of two newly added pipelines, so that hexane flushing operation can be carried out in case switching is completed.