This study aims to propose an approach for determining key Performance Shaping Factors (PSFs) to promote human reliability management during LNG ship offloading process. Offloading LNG from ship to onshore terminal is a high-risk and human-related operation; a small human error may trigger catastrophic consequences such as fire, explosion, and even fatality. Therefore, ensuring high human reliability level is necessary. It is widely acknowledged that human reliability is mainly influenced by plenty of PSFs. If some top important PSFs can be identified, then it will be helpful to human reliability assurance and targeted management for avoiding human errors in the shipping LNG offloading work. Determining key PSFs is a decision-making system, but there is always lack of historical data of PSF. Namely, this decision-making system has strong characteristic of grey, which is an obstacle for finding the significant PSFs. Due to this condition, the grey theory-based Grey Relational Analysis (GRA) method is a choice and should be selected for handling the insufficient PSF data and grey characteristics. Apart from GRA, the definition of risk (frequency products consequence) is utilised as the basis for reasonably explaining the ranking order of each involved PSF. In one word, GRA is firstly conducted from the view of frequency and the view of consequence, then combining the results together to identify key PSFs. The proposed method is applied to a real shipping LNG offloading case. The final result indicates that the proposed method provides a reasonable and effective way to find key PSFs for ensuring human reliability in shipping LNG offloading work.