The study aims to develop an instrument of English students' core competencies practices in learning process. The development used qualitative and quantitative method in different steps and analysis. Sixth steps were applied in the instrument constructions; they were literature studies; defining constructs and sub-constructs; constructing indicators; assessing and judging indicators; defining face validity, confirming content validity, consistency testing and confirming constructs validity. The result came out with three main constructs; soft skills, hard skills and academic character. Soft skills classified into six sub-constructs with 45 indicators. Hard skill was classified into 10 indicators with no classification into sub-construct. While academic character classified into seven sub-constructs with 41 indicators. The instrument suggested to be used to monitor students' practices of Core Competencies in learning activities at Universities. Furthermore, the instrument were developed by refereeing to current literature from some countries, it is expected that the instruments and the method of its' development contribute to area of students' and graduates' core competencies.