Abstract: Quality prevention decision problem in supply chain is studied under different information backgrounds.Based on the quality contracting optimization models in references^[1,2],a principal agent model concerned with quality prevention decision is set up with regards to supplier as principal and buyer as agent.In the models,quality prevention and up-front payment variables are decided by the supplier,quality evaluation variable is decided by the buyer.Focus is on the study of quality prevention decision problem under asymmetric information.Maximum principle is used to get the solution to quality prevention and up-front payment variables when buyer evaluation information is hidden.At last simulation is done concerned with an agricultural machines company’s tractor selling problem.Simulation results under different information backgrounds are analyzed and compared.

Key words: asymmetric information, supply chain, principal agent, maximum principle, prevention, evaluation, up-front payment