Abstract: The present investigation was conducted to assess the effect of environmental gradients on vegetation characteristics, diversity and geographical distribution patterns in five different locations of mountain Musa, Saint Katherine protectorate area (SKP), southern Sinai, Egypt. Vegetation parameters and soil samples were collected from 25 stands distributed in five distinct locations at different elevations (Wadi Al-Far'aa at 1821-1847 meter above sea level, Farsh Al-Shoeibi at 1950-1984 m a.s.l., Farsh Al-Loza at 1985-2000 m a.s.l., Kaneset Al-Hammar at 2001-2023 m a.s.l. and Farsh Eilia at 2024-2031 m a.s.l.) present in Musa mountain area. Five quadrats (5x 5 m each) were set at each stand. Relative abundance, population density and frequency and the relative importance value and the relative importance index (IVI) were calculated for each species. Wadi Al-Far'aa had the lowest plant species density, frequency, abundance and (I.V.I.). It recorded the highest number of plant species (42) and diversity indices (Simpson's index, Shannon–Weiner's index and Brillouin's index). Farsh Al-Loza had the highest density, frequency, abundance and I.V.I., but had the lowest values of both diversity indices and number of families (8). The highest number of families (18) was recorded in farsh Eilia. 62 plant species from 22 families were recorded in this study. Seriphidium herba-album (Asso) Sojak is the most dominant plant species and Compositae is the most common family. The environmental gradients including soil chemical properties, topographic variables (slope, elevation and aspect) and climatic factors (temperature, rainfall, and air humidity are the major influencing factors causing variation in vegetation distribution and plant community structure.