The guarantee of Environmental Flow Requirements (EFRs) of rivers is an important foundation for the sustainable utilization of water resources. By considering the water depth requirement of aquatic organisms and distinguishing the inter-annual difference of EFRs, the traditional ecological hydraulic radius approach was improved. Then the Adapted Ecological Hydraulic Radius Approach (AEHRA) was used to study the EFRs characteristics of two main rivers (Buha River, Shaliu River) in Qinghai Lake watershed using Naked Carp (Gymnocypris przewalskii) as the biological indicator, and the results indicate that (1) EFRs calculated by AEHRA is reasonable and could satisfy the demand for keeping the basic ecological function of rivers. EFRs would be significantly overestimated, if its inter-annual difference is not considered. (2) Annual EFRs of Buha River and Shaliu River were 1.45×10⁸m³-2.64×10⁸m³, 1.26×10⁸m³-1.85×10⁸m³, respectively in the period of 1958 to 2009. (3) Average ecological water shortages of Buha River and Shaliu River were 0.29×10⁸m³, 0.21×10⁸m³, respectively in April and May. Consequently, AEHRA is a new and effectual method for calculating the EFRs of rivers.