To solve the problem that quantitative transfer of viscous liquid between tanks in the sample pretreatment devices couldn't be realized precisely, TRIZ and TOC are integrated for problem analysis and solving. The composition of sample pretreatment device and their relationship are analyzed from the system point of view, and then the core issues of the device is determined under the basis of evolution mode of TRIZ and prerequisite tree of TOC. Based on the modules of the conflict, standard solution and effect in computer-aided innovation software-InventionTool3.0, the choice, evaluation and amendment of design solutions is carried out. Finally, the principle solution to realize quantitative transfer of viscous liquid in sample pretreatment devices is put forward.