The methane tail gas generated within ethylene plants is typically utilized as regeneration gas and fuel for cracking furnaces. During the cryogenic separation process, excessive ethylene is lost to the tail gas, resulting in a high concentration of olefins in the tail gas, which will have adverse effects on the economy and the long-term safe and stable operation of the plant. Based on the ?Front-End Depropanizer and C₂ hydrogenation of Sinopec LECT technology, this paper analyzes that the separation efficiency of C₁ and C₂ in the high-pressure demethanizer system is the primary cause of the olefin concentration fluctuations in methane tail gas. By analyzing the influence of low methane/hydrogen ratio in the cracked gas composition on the separation efficiency of high-pressure demethanizer system, this study explores the measures for enhancing the heat exchange efficiency of the overhead condenser and controlling the amount of ethylene in the methane tail gas by optimizing the operating conditions and locally reconstructing the processes while maintaining the primary separation process unchanged. These measures include adjusting the operating conditions of the demethanizer system, increasing the circulation of methane, and recovering ethylene from tail gas. Additionally, the study compares the impact of various schemes on plant investment and operational energy consumption levels, and establishes several methods for controlling the ethylene concentration in the demethanizer system and the methane tail gas.