The teacher aptitude test is developed as an instrument for selecting candidates for both teacher preparation and actual teaching posts. This test consist of three parts: non-verbal reasoning, teaching attitude and professional knowledge in subjects such as Educational Psychology, Child Development, Principles of Education and Psychological testing and Statistics. Construct validity were obtained by comparing mean scores of students from various grades of 7 normal schools and 3 junior normal colleges in Taiwan. In general, the scores of non-verbal reasoning & those of attitude have no relation with grade changes, but the scores of professional knowledge show a markedly progressive increase with advancing grades. These findings may support the generalization that the test is a very useful tool for the selection of perspective teachers.