Abstract: In order to fully apply the abundant oyster shell resources in Zhangzhou City to the passivation remediation of arsenic (As) and chromium (Cr) pollution in the acidic cultivated soil, the weakly acidic cultivated soil contaminated with As and Cr was used as the research object, and a pot experiment was conducted to study the passivation effects of the application rate of oyster shell powder on As and Cr pollution in soil. Five gradients of oyster shell powder application rates were set up in the experiment, namely, 0 (CK), 0.2 g·kg⁻¹ (Atr 1), 0.4 g·kg⁻¹ (Atr 2), 0.6 g·kg⁻¹ (Atr 3), and 0.8 g·kg⁻¹ (Atr 4). The results showed that after the acid farmland soil was treated with oyster shell powder, the soil pH value increased with the application time. After 60 days of application, the soil pH value with the treatment of Atr 1, Atr 2, Atr 3, and Atr 4 increased by 0.50, 0.83, 1.10, and 1.31 units, respectively, compared with CK. The application rate of oyster shell powder showed a highly significant positive linear correlation with the soil pH value (P＜0.01). The treatment of oyster shell powder had no significant effect on the total content of As and Cr in soil (P＞0.05), but could significantly reduce their bioavailability of of As and Cr in soil (P＜0.05). Compared with CK, the ratios of bioavailable As in Atr 1, Atr 2, Atr 3, and Atr 4 treatment decreased by 2.45%, 3.37%, 3.48%, and 3.66%, respectively, while the ratios of bioavailable Cr decreased by 1.82%, 2.99%, 3.06%, and 3.52%. The passivation effects on the As pollution in soil with the treatment of Atr 1, Atr 2, Atr 3, and Atr 4 were 30.21%, 41.83%, 42.90%, and 45.03%, respectively, and the passivation effects on the Cr pollution were 44.01%, 68.42%, 70.10%, and 80.47%, respectively. There was a parabolic-type variation relationship between the application rate of oyster shell powder and the passivation effect on the As and Cr pollution in soil, with the correlation coefficients (r) of 0.9861 and 0.9893, respectively (P＜0.01). The results of this study showed that the oyster shell powder had good passivation effects on the pollution of As and Cr in acidic farmland soil. When the application rates were 0.62 g·kg⁻¹ and 0.69 g·kg⁻¹, respectively, the effects of passivation and remediation for the As and Cr pollution in soil were best, reaching 47.06% and 79.06%, respectively. The results of this study needed to be further verified in the field production.