Rhizosphere organic chemicals response and its role on Cr/Se adsorption is of great importance to understand Cr/Se bioavailability in Cr contaminated soil with the application of Se. In the current work, the processes were carried out using rhizobox experiment (Brassica campestris L. ssp. Chinensis Makino). The results showed that in soil contaminated by 200 mg kg-1 Cr(III), Se(Ⅳ) complexed with Cr(Ⅲ) and carboxylic acid (cis-9,10-Epoxystearic acid, hexadecanedioic acid) reduced Cr(Ⅵ) to Cr(Ⅲ), thus increasing of Cr adsorption, furtherly, decreasing Cr bioavailability. While, in soil contaminated by 120 mg kg-1 Cr(Ⅵ), Se(Ⅵ) competed for adsorption sites with Cr(Ⅵ) and salicylic acid activated insoluble Cr(III), thus decreasing Cr adsorption, finally, increasing Cr bioavailability. Moreover, with Cr contamination, Se bioavailability in soil was enhanced by the secretion of carboxylic acid, which can reduce Se to lower valent state, compete the adsorption sites and complex with Se oxyanion. These results yielded a better understanding of rhizosphere dynamics regulating by Se application in Cr contaminated soil. Moreover, the current study supplemented the theoretical basis for beneficial elements application as an environment-friendly resource to facilitate cleaner production in heavy metal contaminated soil.