For heavy oil reservoir，steam huff and puff and steam drive are two important stages of steam flooding recovery.The economically recoverable reserves and economic limit of steam-oil ratio are two important indexes to evaluate steam flooding recovery. Up till now，the injection-production relationship method of the national industry standard published in 1996 and 2010 are the main methods to evaluate recoverable reserves of heavy oil reservoir by steam flooding recovery. This method describes the semi-log linear relationship between the cumulative gas injection rate and the cumulative oil production rate and its effective application largely depends on the economic limit of oil-steam ratio（0.25 t/m3 for the steam huff and puff，and 0.15 t/m3 for the steam flooding recovery）. However，the economic limit of oil-steam ratio in the national industry standard is rather higher which leads to smaller technically recoverable reserves. The production decline method was firstly used to predict economically recoverable reserves accurately，and then the injection-production relationship method was applied to predict economic limit of steam-oil ratio. At the same time，the irrationality of the economic limit of oil-steam ratio，the unreliability of the technical recoverable reserves and the incorrectness of the total technically recoverable reserves of the national industry standard were researched and analyzed. The actual application of Block Qi40 in Liaohe oilfield indicates that the economically recoverable reserves predicted by the method in this paper are 1 573×104 t，and the economic limit of steam-oil ratio is 20 m3/t and its corresponding economic limit of oil-steam ratio is 0.05 t/m3. However，the technically recoverable reserves predicted by the economic limit of oil-steam ratio according to the national industry standard is 1 110×104 t，which equals to the cumulative oil production rate of 1 144×104 t in 2005.