The invention relates to a method for system state detection and initial work of a mobile robot. The mobile robot comprises a mobile trolley system, a multi-joint mechanical arm system, a clamp system, a visual ultrasonic detection system and a hazardous chemical solution storage system. The method includes the steps that a mobile robot marching route tape is laid, a key position point is calibrated, a typical program block is compiled, and coordinate system calibration of the multi-joint mechanical arm system is conducted; highly-hazardous environment state detection, mobile robot state detection and manual liquid taking tool preparation are conducted; initial work of the mobile robot is conducted; and the mobile robot enters an idle state and waits for a master console to send a hazardous chemical solution extracting instruction. By means of the method, the mobile robot is used for conducting automatic, quantitative and standard operation of quantitative hazardous chemical solution extracting repeatedly in a highly-hazardous environment, and therefore people can be completely isolated from the highly-hazardous environment without making contact with the highly-hazardous environment, and the requirement for sufficiently detecting the hazardous chemical solution is met.