Low molecular weight polyethylene wax(PE-wax) was used to prepare coating agent for protecting the caking of fertilizer. Viscosity, melting point, and mixed state of the coating agent was investigated. The optimum ratio of PE-wax:base oil:surfactant was 6.8:2.5:0.7. PE-wax with molecular weight of 800 to 1500 was oxidized even at relatively mild conditions. A coating agent with proper melting point, mixed state, and coating state was obtained by using the oxidized PE-wax. It was therefore known that paraffin wax could be substituted with oxidized PE-wax.