Abstract：The purpose of this study was to conduct a diagnostic assessment of athletic performances of compound archers during competition. The research subjects of this study were 10 compound archers from the National Taiwan Sport University. The formal competition results of these archers from November 2017 to November 2019 were collected and taken into the many-facet Rasch measurement model to assess the archers' potential, investigate their unexpected responses during competition, and cross-analyze the individual performance by focusing on the archer facet. Results indicated that: (1) The database of unexpected response from the elite archers is not sufficiently large for statistical analysis on each archer, and only group diagnosis can be done. The analytical likelihood ratio of the ranking tournaments and the rivalry tournaments are 9.691 and 13.474, respectively. Neither value met the significance level. (2) Comparing the unexpected response between the ranking tournaments and the rivalry tournaments, the t-value of .46 does not meet the significance level. This indicates that the data from 2 years' competitions is still insufficient, and accumulating long-term data is required before constructing an analysis program on a scientific basis. We conclude that the method to analyze the archers' unexpected responses in this work is feasible. It enables the investigation of unexpected responses and deviation analysis of cross-facets as an effective basis for diagnostic assessment. (Full text)