LBlock is a 32-round lightweight block cipher with 64-bit block size and 80-bit key. This paper identifies 16-round related-key impossible diferentials of LBlock, which are better than the 15-round related-key impossible diferentials used in the previous attack. Based on these 16-round related-key impossible diferentials, we can attack 23 rounds of LBlock while the previous related-key impossible diferential attacks could only work on 22-round LBlock. This makes our attack on LBlock the best attack in terms of the number of attacked rounds. This paper identifies 16-round related-key impossible diferentials of LBlock, which are better than the 15-round related-key impossible diferentials used in the previous attack. Based on these 16-round related-key impossible diferentials, we can attack 23 rounds of LBlock while the previous related-key impossible diferential attacks could only work on 22-round LBlock. This makes our attack on LBlock the best attack in terms of the number of attacked rounds.