research about the influencing factors on transmissionand transformation construction cost is very important，it helps to control the cost reasonably.According to the whole process management theory, we can figure out the key point parts in every step. Then we introduce the research method about how to build the influencing factors database，moreover，we also give the way about how to put the influencing factors research results into practice. In all, influencing factors research do contribute to the construction cost forecast and controlling.