The paper explored the conditions for retailers to implement option contract and the strategies to make joint purchase in spot market. Under the condition of uncertain market demands, a joint purchase model integrating batch ordering, option contract and spot market has been developed. Considering price fluctuation, the conditions for implementing option contract-based ordering have been studied; the impacts of price fluctuation and option execution price on retailers optimal ordering of joint purchase have been analyzed as well. The result shows that if a retailer adopts a joint purchase strategy, certain constraints need to be met. Otherwise, it is more conductive for the retailer to maximize revenues by adopting a single purchase order. When the spot market is involved, the total order quantity and the order quantity of option contract are negatively correlated with the option execution price and are positively correlated with the spot price fluctuation; and, the order quantity of bulk order contract is positively correlated with the option execution price and is negatively correlated with the spot price fluctuation.