This work attempted to explore the causes of incomplete cleaning on the top of rectangular flat pleated filter cartridges, and designed newly developed slit nozzle to remove the caked-on dust of the dead zone. In this study, 7 slit holes (length 39 mm x width 1 mm) were designed to compare the peak pressures on the surface of the filter with circular nozzle (7 holes per pipe and the diameter of each hole is 7 mm) under the pulse pressures of 0.3 and 0.4 MPa, the jet distances of 20-100 mm, the filtration velocity of 0.8 m/min and the dust mass concentration of 20 g/m(3). The experimental results showed that the optimum distance of circular nozzle was 20 mm, while that of slit nozzle was 20-40 mm, which can enlarge the application range of jet distance. Under the optimum distance, the pressure difference between the upper measuring point P1 and P4 was above 1000 Pa with circular nozzle, while that between the point P1 and P4 was below 400 Pa at the same conditions with slit nozzle. The experimental results also showed when the jet distance was less than 40 min, the residual dust and systematic resistance under slit nozzle were lower than those of circular nozzle. The newly developed slit nozzle overcame the cleaning difficulty on the top of the filter cartridge and was beneficial for the industrial application. (C) 2020 Elsevier B.V. All rights reserved.