In order to identify the adverse effects of salt stress on physiology of spinach leaves, plants were grown in a climate chamber with 22/18 °C (day/night) temperature, 70% humidity, 10/14 hours (light/night) photoperiod and 400 micromole m-2slight intensity conditions. In this research Meridian F1 and San Moreno F1 varieties and in hydroponic growing systems Hoagland nutrient solution were used. Salt applications have been started from the period which plants have 4-5 true leaves and continued to harvested time. The salinity of the nutrient solution in the containers has been set up as EC = 2, 6, 8 and 10 dSm-1. Trial coincidence plots were established with 3 replications and at each repetition including 2 varieties (Meridyen F1 and San Moreno F1) and 4 different salt concentration (EC = control, 6, 8 and 10 dSm-1) were applied. A total of 24 experimental plots in all, a total of 384 plants were grown in 16 plants in each plot and the entire trial. During the experiment, leaf water potential (MPa), leaf relative water content (%), membrane infestation in leaf cells (%), total chlorophyll amount contained in the leaves (SPAD value), and leaf stomata permeability (mmol m-2 s-1) were measured. According to obtained results, Meridian F1 variety has been identified as tolerant on the contrary San Moreno F1 variety has been identified as sensitive against salt stress. Increased salt concentration has shown that leaf water potentials measured before dawn and midday, leaf relative water content, the total amount of chlorophyll in leaves and stomata permeability are reducing, on the contrary the rate of harm produced in the leaf cell membrane is increasing.