Abstract
King Salman National Park is located about 22 km north of Riyadh city (Saudi Arabia) and has an area of 340000 m(2). The park is one of the important parks in Riyadh and the Kingdom of Saudi Arabia. This study aims to determine the floristic structure and plant diversity, informing policymakers and conservationists about this protected area. Fifteen sites of the national park, cultivated and non-cultivated, were selected. Density, frequency and diversity indices were evaluated. Twenty species were recorded in the park, including eight species of phanerophyte (40%), followed by seven species of chamaephytes (35%), three species of therophyte (15%) and two species of hemicryptophytes (10%). Rhamnaceae were dominated in the national park with one species (Ziziphus spina-cristi) which had the greatest ecological importance in all areas under study (44.77%). Small sandy hills have the highest diversity among all studied sites. Decreasing the effect of visitors and climate change by creating protected areas in the park could increase plant diversity in the park under study.