Abstract: In engineering practice, significant differences in heat flux are consistently observed between 40-foot container tanks and experimental cryogenic storage tanks when identical insulation material arrangement schemes are employed. These discrepancies have raised concerns about the applicability of standardized insulation performance metrics across varying tank geometries and operational conditions. Studies have demonstrated that the heat flux of cryogenic tanks with different structural shapes can directly indicate the thermal insulation performance of insulating materials in specific environments. Consequently, this parameter is widely regarded as an effective evaluation criterion for the thermal insulation performance of cryogenic tanks. Multiple factors are identified as significantly influencing heat flux measurements. These include the type of cryogenic liquid stored, the geometric configuration and structural dimensions of the cryogenic tanks, and the characteristics of interlayer heat transfer mechanisms such as residual gas conduction, solid conduction, and radiative heat transfer. The complexity of these interactions necessitates a comprehensive analytical approach to reconcile experimental data across different tank systems. In this paper, a conversion relationship for heat flux is derived for high-vacuum multilayer insulated cryogenic tanks with varying structural shapes and cryogenic liquids. The derivation incorporates key factors including the temperatures of the cold and hot boundaries and the proportional coefficient of the insulation structure. Based on this theoretical framework, a verification method is proposed to assess the feasibility of insulation structures intended for liquid hydrogen tanks using test data obtained in the liquid nitrogen temperature range. This methodology provides valuable guidelines for the engineering design of high-vacuum multilayer insulated cryogenic tanks, ensuring that insulation performance can be accurately predicted and validated across different operational scales and fluid types. The approach not only enhances the reliability of thermal performance assessments but also contributes to the optimization of energy-efficient designs in cryogenic storage systems.