BackgroundThe guardianship ability of guardians of patients with severe mental disorders plays an important role in supporting the patients' recovery and reintegration into society. It is necessary to develop a scientific tool since there is a lack of tools to quantitatively assess the guardianship ability. ObjectiveTo explore and develop an assessment scale for the guardianship ability of guardians of patients with severe mental disorders， so as to provide references for the construction of scientific and reasonable guardianship ability evaluation tools. MethodsA pool of scale items was constructed through a literature review and interviews， followed by two rounds of expert consultation with 15 specialists. 364 guardians of patients with severe mental disorders in Guangzhou were investigated. The scale items were screened and optimized using item analysis and exploratory factor analysis， and the structural validity of the scale was further verified through confirmatory factor analysis. The content validity of the scale was evaluated by item-level content validity index （I-CVI） the average scale-level content validity index （S-CVI/Ave）. The reliability of the scale was tested by Cronbach's α coefficient and split-half reliability. ResultsThe guardianship ability scale for guardians of patients with severe mental disorders consists of 25 items， including three dimensions of guardianship willingness， guardianship knowledge and behavior and guardianship self-efficacy. The results of the item analysis showed that all items met the corresponding criteria and were retained. Validity test： the I-CVI ranged from 0.800 to 1.000， and the S-CVI/Ave was 0.964. Factor load of each item on the corresponding factors ranged from 0.596 to 0.976， and the model demonstrated good fit： chi-square degree of freedom ratio （χ²/df） was 2.444， Tucker-Lewis index （TLI） was 0.908， comparative goodness of fit index （CFI） was 0.917， standardized root mean square residual （SRMR） was 0.049， and root mean square residual （RMSEA） was 0.089. Reliability test showed that the total scale had a Cronbach's α coefficient of 0.966， and the split half reliability coefficient was 0.915. ConclusionThe guardianship ability scale for patients with severe mental disorders developed in this study has good reliability and validity， and has certain application value for the assessment of guardianship ability for patients with severe mental disorders. ［Funded by Health Science and Technology Project of Guangzhou （number， 20221A011049）］