NIRS-KIT is a MATLAB-based cross-platform toolbox for both task and resting-state fNIRS data analysis with a user-friendly GUI. This toolbox covers the entire data analysis pipeline, including data preparation, quality check, preprocessing, individual-level analysis, group-level statistics, and result visualization. For task fNIRS data, individual-level statistical analysis is carried out to detect task-related neural activation based on GLM. For resting-state fNIRS data, individual-level functional connectivity (FC), amplitude low-frequency fluctuation (ALFF), fractional ALFF can be calculated. It can also perform the network metrics analysis by calling Gretna (Wang et al., 2015). For group-level analysis, NIRS-KIT provides several popular parametric models and multiple comparison correction approaches. NIRS-KIT provides multiple visualization functions to visualize the statistical results. Please contact: houxin195776@mail.bnu.edu.cn, if you have any questions.