Adding calcium silicate hydrate seed–polycarboxylate ether (C–S–Hs–PCE) to cement-based materials can effectively improve the early strength. C–S–Hs–PCE can provide nucleation sites for the formation of a hydration product C–S–H gel, effectively promoting the generation of the C–S–H gel, and accelerating the process of cement hydration. The acid-ether ratio is an important structural parameter of comb-type PCE molecules, having an impact on the synthesis and early strength enhancement of C–S–Hs–PCE. This paper investigated the effect of acid-ether ratio on the particle size of C–S–Hs–PCE and the early strength of cement-based materials by using dynamic light scattering (DLS) particle size analysis, total organic carbon analysis, X-ray diffraction, low-field time-domain nuclear magnetic resonance, scanning electronic microscopy, isothermal calorimetry, and compressive strength tests, respectively. The results show that the C–S–Hs–PCE formed at a high acid-ether ratio PCE has a smaller particle size, which is more conducive to promoting the hydration of the silicate phase and the generation of calcium hydroxide and C–S–H gel, thereby accelerating the hydration of the paste, reducing the total porosity of mortar, and improving the early compressive strength of mortar, especially within 24 h.