The new edition of The estimated methods of oil recoverable reserves is the national industry standards released by National Energy Administration on 15th December, 2010. It has been acting on for more than 3 years and is important for the assessment of oil recoverable reserves. The calculation method of oil recoverable reserves is the core part of the standard and has effects on the reliability and availability of the results and also the investment risk assessments. Therefore, attentions should be paid to the calculation methods selection. The calculation methods in the new standard include analogy method, empirical formula method, oil displacement efficiency method, production decline method and water drive curve method. In this paper, the uncertainty and the unreliability of these calculation methods were proposed along with the specific recommendations which can be concluded as follows: delete some empirical formula of less credibility, adopt some overseas empirical formula proved by practical application, modify some empirical and production decline formula, use the methods of linear trial and error, curve displacement, and typical curve fitting to determine the decline type and decline parameters, delete some water drive curves derived from A and B water drive characteristic curve, and add the method of prediction model.