[[abstract]]No matter it is development of new product or production of existing product, before transferring to mass production phase, both need to undergo a so-called “ramp-up” stage, during which yield is still low. Since “ramp-up” is an inevitable phase before stable yield and mass production can be achieved, it is significant to shorten the ramp-up process in order to increase the whole competitiveness of the industry. This study will utilize System Dynamics to investigate factors that affect ramp-up process and create a model for further analysis in a hope to single out the key factors that help shorten ramp-up process. During the model building process, the study is usually diverted into two parts, each leads to the creation of Casual Loop Diagram(CLD) and System Dynamic Model. The CLD is mainly introduced to transform the related factors of a researched topic into graphics to illustrate their causal relation, while System Dynamic Model is introduced to formulate the causal relation of CLD for simulation purpose. When the model is erected, some tests need to be done to verify its credibility. Based on the result of the experiment, the key factors that contribute to the shortening of ramp-up process are product complexity, rework factor, price change coverage, desired inventory coverage, target production. When production line is in the early stage of ramp-up, target production should be significantly reduced to allow sufficient time to overcome potential production problems. When yield becomes gradually stable, the productivity will also grow. The remaining factors can be classified into categories such as product design, production capability, product pricing, and inventory adjustment, etc. Although the adjustability of the remaining key factors is minimal, certain degree of adjustment before mass production will significantly increase the yield.