He began his career as a forester in 1900 as a general guard at Grenoble, then joined the ENEF in Nancy in 1901 first as attached to the Research Station then as a forestry botany lecturer from 1903 to 1941.

[2][3] After his first years as a botanist, Guinier broadened his field of knowledge and action in pedology, genetics, reforestation, pathology and physiology thanks to his interactions with scientists such as Georges Le Monnier, Émile Schribaux, Henri Hitier, and René Maire.

[1] Guinier was the national correspondent of the Academy of Agriculture (Académie d'Agriculture) from 1923 and member in 1936.

In 1929, Guinier was elected president of the International Union of Forest Research Organizations (IUFRO).

He was elected member of the French Academy of Sciences in 1953 in the rural economy section, in the chair of Louis Lapicque (1866-1952).