Abstract: In order to understand the smoke formation characteristics of fresh leaves of landscaping trees during pyrolysis and combustion in fire prevention period, the smoke density of fresh leaves of 13 common landscaping tree species in Kunming area was measured by JCY-2 type smoke density tester.The relationship between smoke yield, maximum smoke density and smoke density of new leaves, near mature leaves and old leaves of 13 landscaping tree species was analyzed. The conclusion can provide a scientific basis for understanding how management measures, intensity and frequency affect the smoke density of fresh leaves pyrolysis and combustion of landscape plants.The studies showed that: the smoke yield of dry leaves per unit mass of plants is new leaves > near mature leaves > old leaves; When the mass of fresh leaves is similar, the greater the water content, the smaller the smoke density level.

Key words: landscaping tree species, fresh leaves, pyrolysis, smoke density