The origin of the ‘rainbow’ in oracle bone inscriptions has been debated in the academic circles, but no final conclusion has yet been found. According to what the ‘rainbow’ in the oracle bone inscriptions looks like, scholars roughly divide it into two categories: the ‘snake’ and ‘dragon’. Reviewing previous argumentations on this issue and resting on comprehensive analysis of various views, this paper traces the academic origin of the ‘rainbow’ in the oracle bone inscriptions, and, at the same time, takes the ‘rainbow’ as the ‘dragon with two heads’, one of the description views on it. Furthermore, it, by means of combining with some arguments over the present archaeological results and discussing again relevant points of them, puts forward an argument that the ‘rainbow’ in the oracle bone inscriptions was taken from the image of the ‘dragon’. On the basis of this argument and relevant theories of philology, archaeology and cultural anthropology, it reinterprets the cultural connotation of ‘auspicious and ominous symbols’ and ‘gender metaphor’, both of which are unique to the special natural phenomenon of the ‘rainbow’ in Chinese culture. Analyzing the cultural meanings such as pouring rain, giving birth to an emperor or a sage, fornication and reproduction, etc. also helps to explain the cultural interconnectedness between the ‘rainbow’ and ‘dragon’ or, more specifically, dragon worship-related cultural prototypes of China.