A portable shape-shifting mobile robot system named as Amoeba II (A-II) is developed for the urban search and rescue application.It is designed with three degrees of freedom and two tracked drive systems.This robot consists of two modular mobile units and a joint unit.The mobile unit is a tracked mechanism to enforce the propulsion of robot.And the joint unit can transform the robot shape to get high environment adaptation.A-If robot can not only adapt to the environment but also change its body shape according to the locus space.It behaves two work states including the linear state (named as I state) and the parallel state (named as II state).With the linear state the robot can climb upstairs and go through narrow space such as the pipe,cave,etc.The parallel state enables the robot with high mobility on rough ground.Also,the joint unit can propel the robot to roll in sidewise direction.Two modular A-II robots can be connected through jointing common interfaces on the joint unit to compose a stronger shape-shifting robot,which Can transform the body into four wheels-driven vehicle.The experimental results validate the adaptation and mobility of A-II robot. A portable shape-shifting mobile robot system named as Amoeba II (A-II) is developed for the urban search and rescue application. It is designed with three degrees of freedom and two tracked drive systems. This robot consists of two modular mobile units and a joint unit. The mobile unit is a tracked mechanism to enforce the propulsion of robot. And the joint unit can transform the robot shape to get high environment adaptation. A-If robot can not only adapt to the environment but also change its body shape. according to the locus space .It behaves two work states including the linear state (named as I state) and the parallel state (named as II state) .With the linear state the robot can climb upstairs and go through narrow space such as the pipe , cave, etc.The parallel state enables the robot with high mobility on rough ground. Also, the joint unit can propel the robot to roll in sidewise direction. Two modular A-II robots can be connected through jointing common interfaces on the joint unit to com pose a stronger shape-shifting robot, which Can transform the body into four wheels-driven vehicle. the experimental results validate the adaptation and mobility of A-II robot.