Abstract：Cucumber fusarium wilt was used as research target．The impacts of adding different concentrations of rare earth element cerium（Cerium chloride）on cucumbers fusarium wilt incidence，the plants growth conditions and the activities of the enzymes related to defense were discussed by pot cultivation experiment．The results showed that cucumber fusarium wilt incidence and disease index were reduced，the plant growth and development was promoted，and the activities of defense enzymes was increased by applying cerium．As cerium concentration increased，the promoting effect increased at first and then decreased as compared with the control．The best effect was 200 mg?L-1 treatment，each cucumber growth index was significantly higher than that of the control．The chlorophyll content，root system activity and proline content（Pro）were increased 85.91%，60.75%，55.77%，respectively．The activities of peroxidase（POD），polyphenoloxidas（PPO）and phenylalanine ammonia-lyase（PAL）were increased by 49.29%，31.50%，80.00%，respectively then the control．Malondialdehyde（MDA）content declined 61.67% than the control.
