A highly effective, economical, and replicable way is imperative to remediate Cadmium (Cd)‐polluted soil. Shell powder is sometimes used to remediate soil contaminated with potentially toxic metals. However, information is limited regarding shell powder assessment. Shell powder is thermally modified at 400, 600, and 800 °C and is added to Cd‐polluted soil for 50 days. The repair effects of shell powder on Cd‐polluted soil are investigated. Compared with the control, the addition of shell powder passivator reduces the content of exchangeable Cd in the soil and converts the exchangeable fraction into other unavailable fractions, especially carbonate‐bound Cd. On average, the value of soil pH increases by one to two units after the application of the powder. Shell powder improves the physical and chemical properties of the soil. Redundancy analysis, entropy method, literature analysis, and theoretical analysis are used for evaluation. Finally, the repair effect score for each treatment group is obtained, and it proves to be a more intuitive method of evaluation. Overall, the results of this study indicate that shell powder is a suitable passivator for the remediation of Cd‐polluted soil. Using a score to express the repair effect is an appropriate evaluation method.