Knapsack sprayers of various types are commonly used in Egypt, especially in small farms, but; performance of most of these sprayers and their ability to be used pesticides accurately and efficiently is poor. Therefore, this research was carried out to overcome some problems of knapsack sprayers, uneven spraying and low field capacity. The research aims to develop and evaluate performance of a boom for a knapsack sprayer to improve spray quality and distribution pattern and increasing the field capacity. The developed boom was tested at different spray pressures, nozzles spacing and height of spray boom. The results showed that; The average values of spray liquid discharge rates for the developed sprayer were 1.29, 1.56 and 1.86 L/min at spray pressures 1.5, 2.0 and 2.5 bar, respectively. For the uniformity of spray volume distribution, the ratio of nozzle spacing to spray height 1:1 was the best for all tested cases of spray pressure due to the values of variation coefficient was less than 10 %, and it's preferable to be nozzles spacing and spray height at 50 cm to increase the performance rate of spraying under all tested pressures. The developed sprayer can be used for spray volume rates from 60 - 80 L/fed. The maximum values of the theoretical field capacity were 1.86 and 1.40 fed/h for spray volume rates of 60 and 80 L/fed, respectively at spray pressure of 2.5 bar, whereas; The maximum values of the effective field capacity were 1.44 and 1.12 fed/h for spray volume rates 60 and 80 L/fed, respectively at spray pressure of 2.5 bar and spraying width of 3.0 m. Also, the average values of field efficiency were 82.20, 80.53 and 78.81 % at spray pressures 1.5, 2.0 and 2.5 bar, respectively. the average values of continuous operating time of the developed sprayer using the battery were 8.27, 5.55 and 3.85 h at operating pressures 1.5, 2.0 and 2.5 bar, respectively.