Two low SNR image sequences energy accumulation algorithms in common use are discussed. One is multi-frames cumulating aiming at slow moving targets, the other is morphological dilation-cumulating aiming at fast moving targets. The hardware implementation based on FPGA of these two algorithms are presented. Experimental result shows that the design has simple structure, clear flow, high running frequency, less periphery components, good expansibility, portability, and has been successfully applied in IR information processor.