Abstract: The calorific value of natural gas is one of the main basic parameters for calculating energy value, which directly affects the accuracy and reliability of energy measurement. At present, it is the most commonly used detection method to analyze the composition of natural gas by gas chromatography, and then calculate the calorific value of natural gas through the composition data, and the accurate analysis of heavy hydrocarbon component (C₆⁺) is the key factor affecting the calculation results of calorific value. This paper summarizes several quantitative methods commonly used to analyze C₆⁺ composition.By analyzing actual natural gas samples, the effects of different quantitative methods of C₆⁺ composition on superior calorific value are discussed and compared. The results show that different quantitative methods have obvious influence on the calculation of calorific value with the increase of C₆⁺ content in natural gas. When the C₆⁺ content in natural gas is greater than 0.1%, the maximum deviation of superior calorific value obtained by different quantitative methods can reach 0.24%. A suggestion is put forward to choose the quantitative method of C₆⁺ composition for natural gas with high heavy hydrocarbon content. The conclusion is of reference significance for the future implementation of natural gas energy measurement in China.