The paper studies a distributor in fresh products supply chain ( cold chain) . The freshness-keeping effort is introduced in order to depict the quantity and quality of the fresh products arriving in the market and the distributor’s optimal decisions. Compared with the previous studies，this paper uses an additive demand function to depict the market demand. Relative enterprise data are used to justify the rationality of this demand function. The paper finds that when the fresh effort is exogenous，the optimal order quantity and the optimal retail price of the distributor are only associated with the freshness-keeping effort. When the retail price is ex- ogenous，the optimal freshness-keeping effort of the distributor depends on the zero point of the first order opti- mization condition of the actual unit cost of the product. When the order quantity is exogenous，the retail price and the profit from freshness-keeping effort increase with the freshness-keeping effort，but the marginal profit from freshness-keeping effort decreases with freshness-keeping effort. Applying the results to Zall Cold Chain， optimal strategies of freshness-keeping effort are suggested.