The article presents the method of calculating critical temperatures for basic components of steel structures according to the design standards (draft) of the Russian Federation "Steel structures - Rules for ensuring of fire resistance", and research a some of other related standards, such as GOST 27772:2021, SP 16.13330.2017, etc., as well as some fire-resistant steel structure design standards: American, Europe, China, Japan, Australia, India. On that basis, develop a method to calculate fire resistance limits for steel structures in accordance with TCVN 5575:2024, TCVN 2737:2023 and some current domestic steel material standards. At the same time, practice calculating the critical temperature for some structural steel members, comparing with the calculation results according to EN 1993-1-2, to confirm the reliability of the applied method. Keywords: In fire; critical temperature; reduction factor of yield strength and elastic modulus.