Abstract: The fact that certain tumors have the tendency to metastasize to specific organs has been recognized for over a century now. First invoked by Paget in 1889, the seed and soil hypothesis suggested that the successful growth of metastatic cells depends on the interactions and properties of cancer cells(seeds) and their potential target organs(soil). We are currently witnessing an increasing amount of evidence, spanning from clinical to laboratory research, which highlight that metastasis is the result of the dynamic balance between the tumor itself and the body environment. Also more and more treatments were developed based on it. In this article, we review the hypothesis and suggest a new theory: Seed can carry, adapt and change the soil. The tumor cells can not only adapt to the microenvironment, but also carry many factors to promote the environment changing. The essence of tumor metastasis is the biphasic effect between tumor cells and microenvironment. Through summarizing the characteristic of breast cancer and colorectal cancer metastasis,this theory has been proved.