Cognitive behavioural therapy (CBT) is a first-line psychotherapy in Western countries, yet there have been limited studies examined the required skills based on perception of CBT therapists in the context of Western countries, and there has been no such research in China. Currently, there is no exist of a selfassessment scale to evaluate the required competence perceived by CBT therapists in China. This study used both qualitative and quantitative method to develop a self-assessment tool by CBT therapist to provide their perception about required skills in the treatment of mental disorders in China. Qualitative research used semistructured behavioural event interviews to identify the essential competences perceived by CBT therapists in China. Based on the qualitative research results, quantitative research was further used to develop a self-rated instrument with 52 questions. Three-hundred therapists who were conducting CBT therapy for clients with mental disorders were invited to participate in the study, 278 of which answered the survey. Among 25 therapists in the qualitative research, three key themes relating to the success of treatment using CBT were extracted from the interview. These themes including generic psychotherapy competencies, common CBT theory, mastering basic CBT techniques are essential skills in the effective application of CBT treatment. Another two themes on challenges and difficulties in the application of CBT include formulating clients’ problems and plans and using CBT techniques properly. Among 52 questions, 44 questions were analysed, which identified four CBT competence related factors: 1. generic psychotherapy competencies; 2. mastering CBT theory and skills; 3. using CBT techniques properly; 4. formulating clients’ problems and plans. The reliability using Cronbach’s α and half-reliability coefficient analysis showed that the therapist competence self-assessment scale had a high level of reliability of 0.94. The content validity, convergent validity and discriminant validity were high, and the structure of the instrument was reasonable. The self-assessment scale may provide a reliable and valid tool to self-assess the required competence and skills perceived by CBT therapists in China, and provide useful information for CBT training curriculum and program in China.