Abstract: The latent heat storage technology based on organic phase-change materials (PCM) can not only perfectly solve the inherent defects of solar energy, but also effectively convert solar energy into thermal energy and store it, providing potential possibilities for application of solar energy systems. Herein, a dual cross-linking encapsulation strategy is proposed to fabricate a multifunctional composite hydrogel (SCP_CMP_DA) integrating photo-thermal conversion, phase change heat storage, and structural stability for solar interfacial water evaporation, using sodium alginate (SA) and carboxymethyl cellulose (CMC) as the hydrogel matrix, n-docosane (C-22) as the phase change material, and polydopamine (PDA) nanoparticles as the photo-thermal agent. The obtained photo-thermal phase-change hydrogel exhibits a high phase change enthalpy of 205.6 J·g⁻¹. Under one standard solar irradiance, the evaporation rate of SCP_CMP_DA hydrogel-based evaporator reaches 1.34 kg·m⁻²·h⁻¹. In the three-cycle test consisting of 60 min of light exposure and 30 min of darkness, the total water production of the SCP_CMP_DA evaporator containing PCM is significantly higher than that of the control group without PCM, demonstrating its capability for continuous water generation during dark periods via heat storage-release temporal regulation. This research provides ideas for the encapsulation of phase-change materials and the design and preparation of corresponding composite phase-change materials, and has important promoting and reference value for the application of phase-change materials in solar thermal energy storage and solar seawater desalination.