Among all the influential factors, the service quality of machine tools is the most important one for workers to decide their machine tools selection in process planning. This paper proposes an evaluation model for service quality of machine tools, aiming to help workers select machine tools on a reasonable basis. An evaluation indicator system of machine tools’ service quality is established based upon a thorough investigation into how the service quality of machine tools manifest themselves. The evaluation indicator system includes the following five aspects: processing cost, processing time, machining precision, green attributes and reliability. The least square method is used to establish an optimization model that determines the weight of indicators based on subjective weight-giving and objective Weight-giving. Finally, a grey relational analysis is conducted to evaluate the service quality of machine tools. Thus we provided an effective decision method for workers to decide their machine tools selection in process planning.