Motivation: In order to expedite oncology drug development to meet cancer patients' need, usually there are lots' of uncertainties when we initiate a phase 3 trial only based on the Object Response Rate (ORR) results or other early endpoint with limited subjects from a single arm Phase I study. The purpose of 2-in-1 Design is to mitigate the risk of a phase 3 study with negative results and save time comparing with conduct a phase 2 study first before phase 3. Method: With one hypothetical oncology trial as example, we applied an innovative 2-in-1 adaptive phase 2/3 design. The 2-in-1 design is to start investment and expectation as a randomized Phase 2 clinical trial, only invest as a Phase 3 after some confirmation from randomized Phase 2 portion are obtained from the phase 2 data. We will go into details about the study design, endpoints, type I error control, timing of the analyses and how to utilize benefit-cost ratio (BCR) to set optimal expansion decision. In addition, Regulatory acceptance and operational difficulties will be discussed.