Screening out highly effective passivators and revealing their arsenic (As) reduction mechanisms are one of the key research focuses in the remediation of As contaminated agricultural soils. Two rice cultivars of Nangeng 9108 and Nei5you 8105 were used as test plants in a pot experiment, the effects of maize straw biochar (MBC), peanut shell biochar (PBC), attapulgite (ATP) and hydroxyapatite (HAP) under the 3% application rates on As content in various parts of rice plants were investigated, and related soil physiochemical properties and the contents of nitrogen (N) and phosphorus (P) in various rice tissues were compared, based on which corresponding As reduction mechanisms were analyzed. The results showed that the passivators significantly reduced As contents in straws and grains of both cultivars (P < 0.001). For the cultivar of Nangeng 9108, the reduction effect of As content in the grains by passivation followed the order of HAP>ATP>PBC>MBC, and HAP>MBC>ATP>PBC for the Nei5you 8105 cultivar. In addition, the levels of As contents in the straws and grains were related to rice cultivars as indicated by the observation that As contents in straws and grains of Nei5you 8105 were significantly higher than Nangeng 9108. MBC and PBC significantly increased contents of soil organic matter and available potassium, MBC and HAP increased the content of soil available phosphorus content. Meanwhile, MBC, PBC, HAP and ATP increased N contents in straws and grains of Nei5you 8105, and increased P contents in straws of Nangeng 9108 and grains of Nei5you 8105. Correlation analysis showed that As content in grains of Nangeng 9108 had a significantly negative correlation with P content in straws, while that of Nei5you 8105 had a significant negative correlation with available P content in soil, P contents in roots and straws, suggesting that the passivators might inhibit rice As uptake through affecting available P content in soil and P uptake by rice. In conclusion, the application of MBC, PBC, HAP and ATP passivators reduced As contents in various rice tissues to different degrees, the most effective with HAP, which can be recommended to use in the remediation of As contaminated soils.