To investigate the effect of planting density regulation on the phytoremediation efficiency of cadmium(Cd)contaminated soil，two Sedum species，namely Hylotelephium spectabile(known as a Cd accumulator)and Sedum aizoon(known as a Cd-tolerant plant)，were selected as the research objects. A randomized block field experiment was conducted to determine the plant growth，Cd absorption，transport，accumulation characteristics as well as remediation efficiency of the two Sedum species under conventional planting mode and dense planting mode. The results showed that reasonably dense planting significantly increased the shoot biomass of H. spectabile and S. aizoon by 206.5%and 218.3%，respectively，in comparison with conventional planting mode. Besides，the shoot Cd concentration，bioconcentration factor and transfer factorof both Sedum species exhibited no obvious different under different planting densities. Moreover，the Cd accumulation in shoot of H. spectabile and S. sizoon reached 114.1 and 60.4 g/hm2，respectively，under reasonably dense planting，which was significantly increased by 121.2% and 180.1%，respectively，in comparison to these under conventional planting mode. The phytoremediation efficiency of two Sedum species under different planting densities was calculated based on either Cd removal amount by plant or Cd reduction amount in soil，respectively. When the remediation efficiency was relatively low，it was advisable to use the plant Cd removal amount for evaluating remediation efficiency. Otherwise，the results by both calculating methods were consistent. The phytoremediation efficiency of H. spectabile was 3.00% and 6.44% under conventional planting and reasonably dense planting conditions，respectively. Therefore，the H. spectabile showed application prospects for actual remediation of Cd contaminated soil and the reasonably dense planting might further promote plant growth without reducing the Cd absorption capacity of plants，thereby improving the remediation efficiency of Cd contaminated soil.