Teachers who can adapt and be ready for all changes will also be able to provide a balance to increase the competence of vocational high school students. This is also not denied when teachers become assessors in student competency tests. The objectives of this study were to produce an instrument for the readiness of teachers as assessors; to knowing good grain reliability; to know the characteristics of the instrument; and to know the difficulty level of the item. The method used in this research is instrument development. Respondents were vocational school teachers who were candidates for competency test assessors. Data collection techniques using a questionnaire. Analysis of construct validity using Confirmatory Factor Analysis. Reliability using Cronbach's alpha. Test the instrument items using the Rasch model. The results are the readiness instruments of the vocational teacher as an assessor has 19 indicators that have been grouped into 5 factors with consistency values being in the same construct (proven construct validity). The result of the calculation of the reliability of this instrument is 0.852, which means that the reliability coefficient is high; There are two items, namely numbers 24 and 18 which indicate the absence of a fit item in the overall item fit criteria; At the item difficulty level, items 8 and 6 have a difficulty score of more than 2, while this indicates that items 8 and 6 have a high difficulty level.