Facing stochastic price-dependent demands, a supply chain with one-supplier and one-retailer was considered. A combined contract with the buy back and target rebate to solve the problem that only the buy back contract or sales rebate contract can not coordinate the supply chain is developed. Two problems were studied. They are: (1) to determine the parameters of the combined contract that coordinate the retailer's action and (2) to evaluate the possible range of the profit allocation between the firms. Numerical examples are given to show that the combined contract can coordinate the supply chain and the impact of demand uncertainty on it.