Abstract: This paper deals with efflux properties of knapsack mister-dusters as well as factors affecting the range of the equipment.Efflux properties of single-phase airflow from the equipment and aerodynamic characteristics of the equipment are analyzed on the basis of the tests. The results show that theory of ideal isothermal free turbulent jet () is applicable to velocity distribution at the fully developed turbulent region in actual airflow of the equipment and to fading effect of velocity at its axis; turbulent coefficient is a key factor affecting the effective range. A constrictor nozzle can uniform the velocity of airflow passing through it, thus being highly recommended to improve the range of equipment. Structure and aerodynamic characteristics of spraying parts and performance of a blower also affect the range greatly. In addition, available power of the blower should be matched with rated power of its engine to reach the full range.This paper provides information for further improvement of the range of knapsack mister-dusters and for development of new products with higher range to meet the needs of forestry as well.