This article presents a new microporous tube-in-tube microchannel reactor (MTMCR) with high throughput and excellent micromixing performance. In the MTMCR, one liquid from the inner tube is divided into many liquid fragments through the microscale pores in the walls, and then these fragments vertically collide with another flowing annular liquid sheet between the inner and outer tubes, generating cross-flow. The annular microchannel allows a mass of fluid to go through it rapidly without enlarging the channel width, thereby achieving a throughput as high as 9 L/min (typical microreactor throughput = 4-100 mL/min). Furthermore, the micromixing performance is expressed in terms of a segregation index, which can be as low as 0.0007. The micromixing time evaluated by the incorporation model reaches the magnitude of milliseconds. In addition, several factors affecting the micromixing such as reactant concentration, flow rate, volume flow ratio, micropore size, and channel width were investigated. The results indicated that an increase of the flow rate, as well as a reduction of the micropore size and channel width, could greatly intensify the micromixing. Therefore, it can be envisioned that the MTMCR would exhibit great potential for various industrial applications in the future.