Complex intervention was first proposed by the British medical research council (MRC) and defined in detail: complex intervention consists of many components, including behavior and its specific parameters (such as frequency, time, etc.), composition mode and implementation method (such as implementer, environment and place, etc.). These components can function independently and influence each other. Each element contributes to the target effect of the intervention, but it is difficult to find out the specific active components in complex intervention. Process evaluation, that is, evaluating the project implementation process, providing the basis for the revision and optimization of projects or programs, and promoting the demonstration and promotion of projects or programs. Process evaluation is often used in combination with effect evaluation to answer the question of whether an intervention is effective, judge the relationship between effectiveness and implementation process, and deeply study the principle of intervention and its influence on outcome.