Abstract: Through the facts that a diesel oil tank collapsed in the storm and then recovered, in theory the paper analyzes the two standards of 《Oil Tank Breather Valve》(SY7511-87) and 《Tank Farm Design Standard for Storage and Transportation System of Petrochemical Industry 》(SHJ-7-88) which the breather valve is selected on the basis of liquid's flowrate principle, which exists that the diameter of breather valve is a bit small and the suction air is not in accordance with the filling air of tank required. The equations on the maximum breathing capacity for breather valve are given by theoretical analyses and calculations, and it is considered that the diameter of breather valve to be selected should be on the basis of the maximum suction capacity of induction valve. It is pointed out that the major cause for tank collapse is the suction capacity induced by heat effect combined theory with calculation case, and put forward a new concept in selecting breather valve-air flowrate principle.