In the photovoltaic industry, measuring efficiency is an important process for manufacturing silicon wafers. The cutting tool gradually wears during the measuring efficiency process. Consequently, the fraction of defectives would gradually become significant. When the fraction defective reaches a certain level, the tool must be replaced. Therefore, it is essential to find out the optimal time to replace the cutting tool for minimizing the fraction defective and reducing the manufacturing cost. In this research, we consider the replacement problem in the photovoltaic industry to obtain the optimal replacement time for the measuring efficiency process. The measuring efficiency process involves multiple product quality characteristics, including the Isc, Voc, and Rsh. In order to maintain the high wafer process quality and to minimize the production cost, we first develop a method for measuring the manufacturing capability of measuring efficiency process. Then, a tool replacement policy is proposed to assess the true capability at each time period of measuring efficiency process and to find out the optimal time for tool replacement.