This article develops and examines an Imaginative Thinking Scale (ITS), a unique measuring method designed to evaluate the development of imagination. According to the studies of the researchers, including Vygotsky, Hill, Coleridge, and others, on the one hand, we elaborately distinguish the cognitive difference between imagination versus fantasy and imagination versus creativity; on the other hand, we present a “gyroscope theory,” based on the concept of Vygotsky's laws of imagination, to illuminate the arousing mechanism of imagination and to establish 4 constructs or subscales, implicit in the ITS, which are initiation, fluency, flexibility, and originality. The ITS consists of 13 open-ended items under these 4 subscales. The participants are 847 first-year undergraduates. Item Analysis and Confirmatory Factor Analysis are used to determine the Cronbach's a test-retest reliability, individual item reliability, component reliability, composite reliability, and construct validity of the ITS. Following a second-order Confirmatory Factor Analysis, the data support the experimental model of the ITS, evolving from our “gyroscope theory,” and can account for .46, .96, .55, and .20 of the variance associated with these 4 subscales: initiation, fluency, flexibility, and originality.