In this study, in situ electrochemical synthesis of a monohydric phosphate intercalated layered double hydroxide was used to treat simulated strontium-containing low-level waste liquids. The removal rate of Sr²⁺ was 99.24% and the adsorption capacity of Zn–Al-LDHs toward Sr²⁺ was 6.01 mg g⁻¹ under the optimal conditions: a current density of 20 mA cm⁻² (Zn electrode), a HPO₄²⁻ concentration of 0.006 mol L⁻¹, a Zn/Al current ratio of 2 : 1, a reaction time of 120 min, a reaction temperature of 60 °C, and an initial pH of 10. The synthesized precipitates were characterized by SEM-EDS, XRD and FT-IR. The precipitate shows the phenomenon of lamellar agglomeration. The XRD pattern indicated that zinc–aluminum hydrotalcite intercalated with a monohydric phosphate was successfully synthesized. The absorption peaks of O–H bonds, O–M–O bonds (M is Zn, Al) and P–O bonds appeared in the infrared spectrum. Therefore, the method of in situ electrochemical synthesis of layered double hydroxides is promising for the removal of strontium in liquid radioactive wastes from nuclear power plants.