Abstract: Alternaria solani is known economically important and the casual agent of early blight on potato and tomato. Identification of plant pathogens is very important in helping to find effective disease control or management methods. Morphology and physiology characteristics of Alternaria solani were investigated for identification and variability. The optimum pH levels of Alternaria solani grow in vitro were 6-7 and the optimum growing temperatures of the isolates recovery in this study was 25 and 30°C. The mycelial width between 0.8-1.5 μm and the conidia are 35-75 μm in length and 10-20 μm in width and 2-7 transverse septa and 1-4 longitudinal septa. This study pointed that there was a variation in the population of Alternaria solani isolated from Jordan valley based on morphology and physiology characteristics.