Onion (Allium cepa L.) is a strong-flavoured vegetable consumed in different ways and its distinctive flavor or simply pungency. Onion has also important natural compounds effective for medical functions. Its importance is directly related with high content of high organosulphur compounds. Shelf life of fresh onion bulb is short enough due to the presence of high moisture content where postharvest loss of onion bulb reaches up to 50% in the production season. Consequentially Onion bulb had extreme variable market price during production and off season which affect both growers and consumers. So in this study the nutritional and volatile components of different drying methods of onion were evaluated. Effect of different drying method on protein, carbohydrate, total sugar, fat, pyurvic acid, ascorbic acid, total phenol, total flovonol, rehydration ratio, colour and sensory properties of onion slice were evaluated and found insignificant at (P < 0.05) for microwave and modified direct solar dryer. But oven drying method had significant effect on onion bulb quality attributes at (P < 0.05) than other two drying methods.