The adsorption method has become one of the most common wastewater treatment methods because of its high efficiency, low cost, non-toxicity, simple operation and so on. The key to the adsorption method is the selection and preparation of adsorbents. As a new type of adsorbent, the layered hydroxide (LDH) has attracted much attention due to its special layered structure, adjustable lamellar elements and exchangeable anions between layers. However, the improvement of LDH adsorption capacity is still an urgent problem. In this work, a novel pyromellitic acid modified layered hydroxide (PA-LDH) was prepared by intercalation modification of ternary Ca-Mg-Al-LDH with pyromellitic acid (PA), and its calcination product (PA-LDO) was obtained by calcining. UV Vis was applied to study their adsorption performance for Orange II. FTIR and BET were used to characterize the morphology and structure of the modified adsorbents. Comparing the FT-IR spectra of LDH and PA-LDH, a new peak of PA-LDH appeared at 1 717 cm^-1, which may be attributed to the C=O group in PA. Moreover, the peak moved towards the high frequency, which may be due to the destruction of the polymer formed between PA, indicating that PA was successfully intercalated into the interlayer of LDH. Compared with the FT-IR spectra of PA-LDH, it could be found that the weak peak of PA-LDO near 3 000 cm^-1 disappeared, implying that the interlayer anion was destroyed during the calcination process. However, the peaks corresponding to the vibration of M—O and M—OH (M=Ca, Mg and Al) at 875 and 723 cm^-1 still existed, indicating that the similar structure was still maintained after calcination. The specific surface areas of PA-LDH and PA-LDO measured by nitrogen adsorption-desorption experiments were 15.934 1 and 119.401 0 m²·g^-1, respectively, indicating that the specific surface area increased after calcination, so that PA-LDO may have a better adsorption effect. With anionic dye, Orange Ⅱ as the target pollutant, the effects of adsorption time, initial dye concentration and other factors on PA-LDH, PA-LDO adsorption performance were investigated by UV Vis under pH conditions 7.0, adsorbent dosage of 5 mg and wavelength of 484 nm. The Qmax of PA-LDH and PA-LDO for Orange Ⅱ were 561.322 and 1 401.639 mg·g^-1, respectively, which were relatively higher than those reported in the literature. Through isothermal adsorption experiments, it was found that the adsorption of Orange Ⅱ by PA-LDH and PA-LDO basically accorded with the Langmuir model, which showed monolayer adsorption was the dominant process of the adsorption process, the theoretical maximum adsorption capacities were 588.235 and 1 428.571 mg·g^-1 respectively, which were close to the experimental values mentioned above. This indicated that the layered hydroxide modified by aromatic acid anions had good adsorption performance for anionic dyes and a certain application prospect in the treatment of dye wastewater.