Onion (Allium cepal L.) is a major commercial vegetable crop grown in almost all parts of the world. In Ethiopian the postharvest loss of onion bulb crop was estimated to be 50% during the production season. So to reduce this postharvest loss of onion bulb determining and employing appropriate storage conditions play an important role. Appropriate storage condition reduces the physiological quality which intern reduces the physicochemical and phytochemical properties of onion. In this study physicochemical and phytochemical properties of onion bulb were investigated under different storage temperature. Onion bulbs were stored at three different temperatures the following quality attributes of onion bulb like glucosidase content, pyruvic acid, flavonoid, dry matter and sugar content were determined for storage period of six months. Quality deterioration of onion bulb was higher at storage temperature of 25 °C while storage temperature 5 °C was found an ideal condition with keeping the quality of onion bulb acceptable. In all the three storage temperatures sugar content show pyruvic acid, glucosidase and sugar content show irregular pattern. Bombay red onion bulb was stored for six months without significant change of quality attributes of onion bulb at storage temperature of 5 °C.