Deemed sales of VAT and not deductible input VAT are very difficult in the study of value-added tax, which are also confuse in the process of practical application, judging an economic business belongs to deemed sales of VAT or not deductible input VAT in the law theoretical study and practical operation of value-added tax is extremely important. In this article, it comes to the conclusion that the specific principles and standards of judgment through analyzing of eight rules of deemed sales of VAT and five rules of not deductible input VAT in value-added tax based on the principle of value added tax.