Abstract: The coconut leaves were used as samples analysed effects of incinerating time on assaying content of K,Ca,Na and Mg in coconut leaves .With low temperature and different time high temperature for incnerating coconut leaves, it was assayed that contents of K、Ca、Na and Mg in the samples on Atomic Absorptive Spectrophotoneter. The results showed as below: For assaying contents of K,Ca,Na and Mg in coconut leaves ,respectively, the optimum time of high temperature for incnerating was 2h、2.5h、2h、2.5h . However, for assaying the coconuts of these four elements at the same time, the optimum time was 2.5h. Meanwhile, it was showed that the recovery rate of elements were 95%-106.3% at 2.5h of high temperature incinerating.