Resumo. Climate is the synthesis of meteorological elements observed during a long time and it has a close relationship with vegetation. Holdridge climatic classification defines representative life zones by different regions on Earth, which explain all these meteorological elements. Therefore, this study has aimed a classification of Rio Grande do Sul state according to Holdridge life zone system by seeking to compare with Köppen climate classification system and vegetation that occurs in the state. That was possible to calculate and determine the life zones for the 496 cities of the state by a minimal sequence of not continuous 25 years of rain and temperature data from 1950 to 1990. Thereby eight life zones were found for the state, which ones has detached: temperate moist forest (74,0%); temperate wet forest/moist forest (13,8%); temperate moist forest/wet forest (8,0%). Holdridge and Köppen relation has shown correlation above 90% in seven of the eight life zones found (87,5% of the state territory), predominantly with climatic type Cfa (humid subtropical, without dry season, with hot summer). Steppe and Steppe-Savanna regions got correlation of 100% with life zone temperate wet forest and its respective transition zones with temperate moist forest. Holdridge life zones system has shown an important tool for agriculture and forestry zoning in this state once there was a satisfied interaction while comparing with Köppen climate classification system and some phytogeographies.