Frequency selective fading caused by chromatic dispersion (CD) and direct detection is the primary impediment for IM-DD systems in achieving a large capacity-distance product. Gerchberg-Saxton (GS) based electrical dispersion pre-compensation (pre-EDC) schemes enhance IM-DD systems' robustness against chromatic dispersion (CD), but their high computational complexity limits practical implementation. In this Letter, a novel, to the best of our knowledge, low-complexity pre-EDC scheme enabled by the cluster-assisting look-up table (CLUT) technique is proposed to further reduce the computation complexity of the non-iterative FIR-based pre-EDC scheme, in which convolution operation is replaced by tables look-up and accumulation processing. And a key strategy is proposed to balance the number and the total size of the LUTs by establishing LUTs for each cluster center after clustering the tap weights. To validate the effectiveness of the proposed scheme, we experimentally demonstrate the transmission of 80 Gbit/s PAM-4 signals and 100 Gbit/s PAM-6 signals over 20 km standard single-mode fiber (SSMF). The experimental results show that the proposed scheme can eliminate the multiplication in convolution operations and reduce the addition times of 58.54% for PAM-4 and 51.22% for PAM-6 signals at the BER of 7% HD-FEC threshold without any penalty.