Abstract: To investigate the strength design of the plate-fin heat exchanger header based on energy criteria, the calculation methods of plastic load based on Ratio plastic work curvature (RPWC) criterion and Plastic work curvature (PWC) criterion are compared. The plastic pressure results determined by both criteria for the header indicate that large deformation effect will strengthen the structure. The comparison of the plastic pressure results for the header with five opening ratios ranging from 0.2 to 1.0, indicates that PWC zero curvature plastic pressure is the largest, RPWC plastic pressure is the second largest, and PWC engineering plastic pressure is the smallest; The ratio plastic work corresponding to the RPWC plastic pressure is less than that of PWC zero curvature plastic pressure. The RPWC criterion with strict critical plastic index is more conservative, simpler and more intuitive than PWC zero curvature criterion, and is thus suitable for such complex structure as the plate-fin heat exchanger header for calculating plastic load, while PWC engineering plastic load suggested can be used as the conservative approximation of plastic load for engineering design.