Involutive lightweight block cipher (IVLBC) is a lightweight block cipher algorithm specifically designed for resource-constrained internet of things environments. An meet-in-the-middle attack of 10-round IVLBC-128 based on mixed-integer linear programming (MILP) improvement was proposed. Firstly, the structural characteristics of IVLBC were studied, and an automated search model of mixed integer linear programming was established to find 10 5-round IVLBC-128 meet-in-the-middle distinguishers. Secondly, the redundancy of the key expansion scheme of this algorithm was studied. According to the principle of minimizing the guessed key bit number in the analysis process, 1 meet-in-the-middle distinguisher was selected, and this distinguisher was followed by 1 round, then 4 rounds, to construct a 10-round IVLBC-128 meet-in-the-middle attack path. Finally, the key was recovered based on this path. The overall analysis requires a time complexity of $ {2}^{123.26} $ encryptions, a data complexity of $ {2}^{61} $ chosen plaintexts, and a memory complexity of $ {2}^{77} $ 64-bit blocks. This result has improved the previous public optimal meet-in-the-middle attack result of IVLBC-128 by two rounds.