In this work, emphasis was placed on the design of a novel nanocomposite for thermal energy storage in the field of green building constructions. Calcium silicate hydrate (C-S-H),the primary product of cement hydration, was firstly introduced as mesoporous accommodations for lauric acid, from an experimental and theoretical prospective. In detail, C-S-H@LA composite was systematically examined through experiments, in terms of Scanning Electron Microscope, Transmission Electron Microscope, Brunauer-Emmett-Teller gas sorptometry, Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimeter. Results demonstrated C-S-H@LA was one promising composite PCM with 32.04 kJ kg(-1) latent heat capacity, 0.514 W m(-1) K-1 thermal conductivity and 91.04% energy storage efficiency. No chemical bonds were found between C-S-H and lauric acid. Notably, stability of C-S-H@LA embracing structural, chemical and thermal properties were also verified. Innovatively, molecular simulation was applied to explain the melting behavior of C-S-H@LA that could be divided into three stages, i.e. acceleration period, stationary period and secondary rising period, based on diffusion coefficient. This work has emerged some new design rules for PCMs fabrication.