Some essential parameters (header losses %, length of cut neck cm, head pulling before cutting % and header efficiency %) were measured in this investigation when harvesting sunflower crop at seed moisture content of 22.35, 15.15 and 10.75 %wet basis , combine forward speed of 2.40, 2.82, 3.30, and3.80 km/hr, reaping direction with the directions: d1 = N  S, d2 = E W, and d3 = WE. Based on these parameters ,the header system for a cereal crops harvester (longitudinal axial-flow , with standard 5 bats reel (T) type CICORIA combine harvester was modified and tested. The demonstrated results for the tests showed that the suggested harvesting direction was d1. Simultaneously, at all the investigated directions the moisture content of the sunflower seeds had a positive relationship with head pulling before cutting % and header efficiency % while reversible correlation was found with the length of cut neck cm and the header losses % . Also, both the header losses % and the head pulling before cutting % increased as increasing combine forward speed with the modifying header.