The invention discloses a high-solid-content ether slump-retaining polycarboxylate superplasticizer preparation method. The method includes steps: dissolving isopentenol polyoxyethylene ether into water, heating at 60-80 DEG C to melt, cooling to 20-30 DEG C, sequentially adding pre-prepared chain transfer agent solution and initiator A solution, adjusting stirring speed to 200-300r/min, dropwiseadding singly or doubly, wherein monomer-containing solution is subjected to dropwise adding for 2.5-3h, and initiator B solution is subjected to double dropwise adding for 3-3.5h, the first 1h reaction temperature rise in a reactor is controlled to be lower than 4 DEG C in a reaction process, and the whole reaction temperature does not exceed 40 DEG C; keeping the temperature for 1-2h after dropwise adding, and adopting caustic soda flakes to adjust product pH value to 7+/-1 to obtain high-concentration ether slump-retaining polycarboxylate superplasticizer mother liquor in solid content of 80% and in state of thick liquid. Concrete mixed by adoption of the superplasticizer is great in slump retaining performance, and cost in production, transporting and storage processes is saved. In addition, products are green, environmentally friendly and free of formaldehyde, and discharging of waste gas, wastewater and industrial residues in the production process is avoided.