Suppression of the immune system is a reaction that can be done to treat various diseases,so we suppress the immune system and allow the body to graft the transplanted organ. Immune-suppressing druge are drugs that help weaken the immune system.In this study, a reliable, sensitive and simple technique was developed for preconcentration and determination of trace levels of azathioprine using solid phase extraction method and detection with visible-ultraviolet spectrophotometer has been presented. Graphen oxide nanoparticles were used as adsorbents for extraction Azathioprine from the sample solution. Azathioprine solution was mixed with solid adsorbent and stirred by a magnetic stirrer .after extraction , the solid phase containing azathioprine was washed by methanol (as a desorbing solvent) and then the adsorption of the extracted analyte was measured at 274 nm. The effective parameters on the extraction efficiency including pH, adsorption and desorption time, rotation speed of adsorption and desorption magnetic stirrer, volume of extraction solvent, adsorbent weight were investigated. Under the optimumconditions, the enrichment factor and recovery were 54 and 86.4% respectively. The calibration curve was linear in the range of 0.008 -1.02 mg 𝐿 −1 with correlation coefficient of 0.9995. the detection limit was 0.008 mg 𝐿−1 and relative standard deviation(RSD) for azathioprine measurment was 2.3%. the application of the method for extraction and determination of azathioprine was demonstrated in real sample.