This paper is aimed to analyse the problem associated with quality in a two-stage supply chain with one supplier and one manufacturer. Most cases in real life is not this simple, although for the propose of keeping easy for calculations, even if there’re several suppliers we can simplify it to only one supplier that provides different quality level products. A mathematic model is built to simulate the problem and we will analyse the problem into two real cases, which will be detailed in the paper. Finally, we aimed to get some conclusions from these cases.