The purpose of this paper is to present new dynamic approaches to evaluate the ERP benefits. We use eight financial indicators to measure the sample entities which implemented ERP between 1996 and 2003 in China. New dynamic approaches about ERP impact of time and impact of company size are suggested for the testing hypothesis of ERP impact. From the field study we find that China and Taiwan have no significant different for the performance of ERP. That is, the financial performance did not reach the goal as it expected. For the Taiwan experience, most enterprises will meet the temporary decline situation after implementing the ERP, but in the long-term, about 4 years, it will make a significant financial progress. That is ERP exhibits the time lag prosperity.