This paper reviews the changes in the different analysis levels of entrepreneurial orientation (EO) and addresses four advantages of firm-level perspective. Focusing on the academic debate on the firm-level EO construct, the Covin-Slevin model is introduced, followed with Zahra's critique and modification, then a response from Covin and Slevin is generalized. The paper concludes that the reason for this academic debate is the different understanding on the nature of EO between scholars. Further research directions are finally suggested.