Abstract: Pressure-compensating emitter is widely used in the agricultural irrigation due to its better compensation and higher uniformity performance than non-pressure compensating one. However, the factors that influence the hydraulic properties of pressure-compensating emitter are complicated, which causes difficulty in design and optimization of the structure of the pressure-compensating emitter. In this study, we determined important influential factors of pressure-compensating emitter based on theoretical analysis and investigated effects of those important factors on its hydraulic performance in laboratory tests. Single factor and orthogonal experiment designs were carried out to analyze the each factor's and their interactive effect. The HydroPC cylindrical pressure-compensating emitter with orifice inline was purchased from PLASTRO. It had working pressure of 60-350 kPa, flow rate of 1.2 L/h, outlet distance of 2.8 mm, cavity diameter of 6.8 mm, boss height of 0.1 mm, groove width of 0.35 mm, boss diameter of 2 mm, diaphragm hardness of 30 HA, and diaphragm thickness of 0.85 mm. The theoretical analysis showed that the hydraulic performance of the emitter could be affected by the distance of outlet from inlet, the outlet diameter of the pressure regulating cavity, the height of the boss in the regulating cavity, the diameter of the boss in the regulating cavity, the width of the boss in pressure regulating cavity, the materials characteristics of the diaphragm such as hardness and thickness. The hydraulic performance experiment of single-factor design showed that: 1) The far distance of inlet from outlet could result in poor flow regulating performance of the emitter since the flow rate tended to be reduced with high working pressure; 2) When the pressure regulating cavity diameter was 00.5 mm, the emitter had good compensating performance and also high initial pressure, which suggested the diameter should be less than 0.05 mm under non-micro drip irrigation; 3) Boss height had a large influence on pressure-compensating performance and its optimal value was 0.2 mm; 4) Boss height did not greatly affect hydraulic performance of the emitter and the performance was almost same when its value was high than 2.0 mm; and 4) The large value of groove width could facilitate pressure-compensating process but not the flow regulating performance. The orthogonal experiment revealed that the hydraulic performance of the emitter was optimal with flow exponent of 0.02795 and initial pressure of 25 kPa when its boss diameter was 2.0 mm, groove width was 0.35 mm, outlet distance and diameter were 2.0 and 0.8 mm, boss height was 0.1 mm. In addition, the material properties of the diaphragm could greatly affect pressure-compensating performance and the performance was best when the hardness of diaphragm was 50° and the thickness was 0.7 mm. In sum, those factors should be considered in design of pressure-compensating emitters. The results would provide important data for emitter design.