In this work, a formal study for Verbal Idioms (VI) of Chilean Spanish is proposed with the objective of developing a computational algorithm for the automatic analysis of texts. For this, the VIS included in Diccionario de uso del espanol de Chile were described according to the lexicon-grammar theory. Then, a computational modelization was made using NooJ, a program that has several utilities. This method was evaluated with an automatic recognition in a corpus composed by texts from Chilean press. 96.4% of precision, 92.23% of coverage and 94.53% of F-measure were obtained. The results show that the algorithm designed is adecuated for the automatic analysis of the VI.