Abstract: During the thermal processing of sea cucumbers, changes in the CFs structure affect their textural characteristics and can lead to certain nutritional losses. To clarify the effect of different Ca²⁺ concentrations on the CFs structure under thermal treatment, the two-step thermal processing method for ready-to-eat sea cucumbers was simulated, using two curing conditions: low-temperature tenderization (37 ℃, 1 h) followed by heat treatment (80 ℃ and 100 ℃, 1 h each). Initially, the study focused on the body wall tissue of sea cucumbers incubated with Ca²⁺, measuring the amount of protein and polysaccharides leached out under different concentrations of Ca²⁺. Subsequently, the extracted CFs were served as a simplified model, and after undergoing the same thermal processing, the contents of protein, polysaccharides and TCA soluble oligopeptides in the dissolution were determined by BCA, phenol sulfuric acid and Folin-method, respectively. The structural changes of CFs were analyzed by DTG and FTIR. The results showed that the higher the thermal processing temperature, the higher the dissolution amount of protein and polysaccharide. When the thermal processing temperature was the same, the contents of tissue blocks and CFs dissolved solution were less at 5 mmol/L Ca²⁺ concentration, the results at 40 mmol/L Ca²⁺ were the opposite, with macromolecular proteins gradually degrading into smaller molecular bands. Under different thermal processing temperatures, the amide I band and amide A band of CFs treated with 40 mmol/L Ca²⁺ showed red shift. Conversely, the amide I and amide A bands of CFs treated with 5 mmol/L Ca²⁺ at 100 ℃ showed blue shifts. Furthermore, lower concentrations of Ca²⁺ correlated with higher thermal decomposition temperatures of CFs. Therefore, thermal processing disrupted the structure of CFs, with low concentrations of Ca²⁺ protecting the body wall and CFs structure, while high concentrations of Ca²⁺ promoted the leaching of protein, polysaccharides, TCA-soluble oligopeptides, and CFs degradation. The findings established a foundation for elucidating the bidirectional mechanism of Ca²⁺ on CFs structure and enriching the theoretical framework for quality control in the thermal processing of sea cucumbers.