Aim To investigate the effect and possible mechanisms of the different concentrations of magnesium ions on aortic rings calcification induced by high phosphorus in rats. Methods Aortic rings were isolated from rat thoracic aorta and cultured in vitro, and randomly divided into control group, high phosphorus group and magnesium intervention group(final concentrations of magnesium ions were 1,2 and 3 mmol/L). Aortic rings were cultured with 10% fetal bovine serum in control group. After 14 days of intervention, the expressions of L-type calcium channel (LTCC)α_1c β₃ subunit, Runt-related transcription factor 2 ( Runx2 ) and smooth muscle 22α ( SM22α ) were detected by Immunohistochemistry. Calcium concentration of aortic rings was measured by Von Kossa staining and quantification of calcium. Results Compared with control group, calcified nodules in high phosphorus group was increased, and calcified nodules gradually reduced with the increased magnesium ion concentration in the intervention group. The expression of LTCCα_1c、β₃ subunits in high phosphorus group increased (P<0.05). With the increase of magnesium ion concentration, the expression of Runx2、LTCC α_1c、β₃ decreased (P<0.05) and the expression of SM22α increased (P<0.05) in high magnesium group. There results of Pearson correlation analysis showed that SM22α was negatively corelated with Runx2(r=-0.671,P=0.001),and LTCCα_1c subunit was positively corelated with Runx2(r=0.712, P<0.001), LTCCβ₃ subunit was positively corelated with Runx2(r=0. 0.692, P<0.001). Conclusion Magnesium can promote high phosphorus induced rat aortic rings calcification, and its mechanism is possibly achieved by downregulatiing LTCC α_1c β₃ protein expression, and reducing the transformation of VSMCs into osteogenic/osteogenic phenotype.