This study examines and analyzes the Palestinian party system after the establishment of Hamas movement. Because the Palestinian party system operates within two internal and external environments, the researcher used the System Theory of David Easton so as to analyze the internal and external factors affecting the Palestinian party system. After discussing the emergence of the most important Palestinian parties, their thoughts and development, the researcher moved to identify the most important elements of the internal and external environments, where the impact of media, civil society, clans, the Israeli occupation and the foreign interference on the Palestinian party system were examined.