This paper have discussed the concept of remaining recoverable reserves of Oil and Gas, the nature, the common methods to evaluate and the parameters applied,and explained the relationship among reserves and the relationship between reserves and it's economic value. In order to get integrated into the world, it may be imperative to list the economic recoverable reserves in reserves report. Except applying the decline method to production prediction during evaluating the economic recoverable reserves, we should also consider the effect of following evaluating parameters,such as operational cost and expenditure, tax related to production, developing expenditure, petroleum product prices, discount rate etc.