The preparation of the CaAl/HC composite was carried out with a supporting material in the form of hydrochar from duku skin. The success of the preparation was demonstrated by XRD, FT-IR, and BET analysis. The diffractogram of CaAl/HC showed diffraction peaks at 2=10.16(003), 18.0 (002), 20.15 (006) and 65.4 (110). The diffraction showed similarity to diffraction in CaAl and hydrochar double layer hydroxyl. The FT-IR spectrum of CaAl/HC also showed similarity to the CaAl/HC double layer hydroxyl at 3448, 1635, and 1381 cm-1. The characteristic spectrum of the hydrochar also appeared in CaAl/HC at 20.15. BET analysis showed an increase in the surface area of CaAl/HC before modification of 11.842 m2/g and increased to 22.635 m2/g of CaAl/HC. The ability of CaAl/HC as an adsorbent is determined through several parameters including selectivity, regeneration, isotherm, and thermodynamics. The results of dye selectivity showed that CaAl/HC was more likely to absorb MR dyes in a mixture of dyes (DG, MO, PR, MR, CR, and DR). The regeneration results showed the ability of CaAl/HC which lasted up to 73.26% in the fifth cycle.