Abstract: Hole group processing is an important process of plastic mold manufacturing. In this paper proposed an improved optimization method based on ant colony algorithm to solve the problem of core hole processing in plastic mold, the initial parameters were optimized by orthogonal test, and the improved ant colony algorithm is used to optimize the processing path of the plastic mold core hole group, so as to solve the problem of too much air travel and low processing efficiency in the large-scale irregular hole group processing. Compared with the standard genetic algorithm and ant colony algorithm, average hole group processing path was reduced by 6.0% and 2.4%. It is 50.1% shorter than the traditional batch processing path. The actual path optimization efficiency is better and the machining efficiency is improved.