Abstarct: The aim of this experiment was to study the effect of ultrasonic waves and spraying salisilic acid on growth and yield of cowpea in drought stress. The experimental design in Shahrood University ؛Agriculture Research Station in 2014 as a factorial randomized complete block design with three replications.Treatments consisted of three levels of seeds exposure with ultrasonic waves, in three levels of zero exposure, 4 and 8 minutes , salisilic acid spraying in two levels including control and spraying the value of one milimolar a week after flowering and a week in the dought stage onwards and two levels of drought stress applied including control and irrigation after flowering. Results showed that applying salisilic acid significantly increased dry weight of pod and grain, number of pod and grain, weight of 100 grains, grain and biological yield, relative water content (RWC), photosynthesis pigments and protein percentage as compared to controls. Ultrasonic waves also increased dry weight of shoot, number of pod and grain, number of node, leaf area (LA), distance of first pod from soil surface, grain and biological yield, chlorophyll content of leaves and protein percentage as compared to control. Also all of the reviewed factors except several exception than drought stress showed a negative impact. It was concluded that applying salisilic acid and also, 4 minutes exposure to ultrasonic waves are useful to improve growth and yield of cowpea.