Alexey Sergeyevich Yermolov was born in Tiflis on November 24, 1847, in the family of Sergey Nikolayevich Yermolov and Maria Grigoryevna, née Gezhelinskaya. After graduating from the Imperial Alexander Lyceum, he began working in the Department of Agriculture of the Ministry of State Properties while simultaneously studying agricultural sciences at the St. Petersburg Agricultural Institute, where he earned a degree as a candidate of agriculture.

Yermolov was appointed senior editor of the statistical department of the ministry and a member of the scientific committee. He led an expedition to study sheep farming in Russia, the results of which were published under his editorship. In 1883, Yermolov became the director of the department of non-tax revenues of the Ministry of Finance, where he helped strengthen the connection between winemaking and agriculture, which was enshrined in the law of 1890.

In 1892, Yermolov was appointed deputy minister of finance, and in 1893 he became the head of the Ministry of State Properties. He was tasked with transforming this ministry into the Ministry of Agriculture, which he successfully accomplished. Historian I. I. Voronov noted that Yermolov was the most competent but least influential minister in the history of the Ministry of Agriculture. He led the ministry until its transformation in 1905.

Yermolov paid attention to agricultural education, handicrafts, improving state mineral waters, and cultivating areas on the Black Sea coast of the Caucasus. In 1886 and 1888, he served as vice-president of the Imperial Free Economic Society and published articles in specialized publications.

In 1902, Yermolov became the chairman of the committee for the development of the Black Sea coast. He also headed the Central Committee for assisting the population affected by the crop failure in 1906-1907. In 1908, he represented Russia at the International Agricultural Institute in Rome and initiated the creation of Russian-Belgian and Russian-Italian chambers of commerce.

From 1906 until his death, Yermolov was a trustee of the Imperial Alexander Lyceum. In his book "Organization of Agriculture," he proposed solutions for peasant crop rotations, which influenced German agrarian theorists.

Yermolov applied his knowledge at the estate of Bolshaya Alyeshnya near Ryazhsk, where he established a horse breeding farm. In 1896, he supported the construction of the Primorsko-Sestroretskaya railway and a resort at the mouth of the Sister River. He allocated land on the coast of the Gulf of Finland for charitable institutions.

In Sestroretsk, streets, a boarding house, a church, a theater, and a beach are named after him. The area along the avenue was called Yermolovka, and the renaming did not affect these places.