Mirror movements (MMs) are often overlooked in patients with amyotrophic lateral sclerosis (ALS). Although the contralateral co-movement (COMO) test can be used to evaluate MMs in patients with ALS, it lacks a systematic evaluation. The aim of this study was to validate the effectiveness of the Chinese version of the COMO test in a Chinese ALS population.We prospectively enrolled 173 patients with ALS as the disease group and 28 healthy individuals as controls. All participants were evaluated using the Chinese version of the COMO test. Univariate analysis and multiple linear regression were used to compare differences between groups. Subgroup analysis of the COMO scores was performed based on different disease characteristics.The COMO score in the ALS group was significantly greater (5.00% [1.67-10.00]) than that in the healthy control group (1.67% [0.00-3.33]). After adjusting for confounders, this difference remained significant. Multivariate linear analysis suggested that the upper motor neuron (UMN) score independently predicted the COMO score (P < 0.001). The COMO score was not affected by different onset regions or lateralizations. Propensity score matching revealed no significant difference in COMO scores between uninvolved limb segments and the corresponding limb segments in other patients. The Cronbach's α of the Chinese COMO test was 0.621.The Chinese COMO test can serve as a potential tool for assessing MMs in Chinese patients with ALS. The UMN score is a factor influencing the COMO score. The COMO test can provide objective evidence for ALS characteristics and the severity of UMN damage.