Abstract: Uncooperative behaviors of contractors caused by environmental uncertainty during contract conduction is one of the key factors which lead failure of Complex Products of System (CoPS) project. In this paper, effects on uncooperative behaviors of CoPS contractors caused by environmental fluctuation, which is divided into market price change and product cost change, are studied. Firstly the revenue functions of buyer and seller in the case of price decline are discussed, the logic relationship between each variables and price decline is revealed, constructs the replicator dynamics equation is constracted, the evolutionary path of user's uncooperative behavior is analyzed, and cooperative threshold and uncooperative threshold which are decided by the degree of price decline are concluded. And then the seller's uncooperative behavior in the case of cost up is analyzed in the same logic of price decline. Finally, numerical simulations are used to demonstrate the effects of different initial conditions of values on the evolutionary path. It is found that:(1) All the variables in revenue functions of both contractors are related with the degree of the price decline when price declining, and all the variables in revenue functions of both contractors are related with the degree of the cost up when cost growing. (2) The relationship between buyer's behavior and price decline:the evolutionary result is cooperative strategy when price decline is less than the threshold of buyer's cooperative strategy (we calls as "buyer's cooperative threshold"); the evolutionary result is uncooperative strategy when price decline is higher than the threshold of buyer's uncooperative strategy (we calls as "buyer's uncooperative threshold"); however, the evolutionary result depends on seller when price decline is between the "buyer's cooperative threshold" and the "buyer's uncooperative threshold". (3) The relationship between seller's behavior and cost up:the evolutionary result is cooperative strategy when cost up is less than the threshold of seller's cooperative strategy (we calls as "seller's cooperative threshold"); the evolutionary result is uncooperative strategy when cost up is higher than the threshold of seller's uncooperative strategy (we calls as seller's uncooperative threshold); however, the evolutionary result depends on buyer when cost up is between the "seller's cooperative threshold" and the "seller's uncooperative threshold". Study reveals the non-linear relationship between uncooperative behaviors and price falling or cost rising, and identifies the cooperative threshold and uncooperative threshold of both seller and buyer. The study provides a new perspective for contractual governance in CoPS and similar project management context under environment uncertainty. The study can provide decision support for management practice to improve the success rate of CoPS and similar project by governing uncooperative behavior caused by environment uncertainty.

Key words: environment uncertainty, price fluctuation, cost fluctuation, uncooperative behavior, contractual governance, complex product of systems (CoPS), evolutionary game