Auxins are phytohormones, which have been shown to be involved in a great number of diverse plant growth phenomena, such as ovary growth, cambial activity, production of ethylene, and effect on the cell wall. Numerous researches show that auxins also exist in algae and play functional roles in their growth and development. Based on the research results in China and abroad, this article systematically introduces the studies on algae auxins, on their contents, distribution, chemical structures, physiological responses, origin and metabolism. The techniques of their isolation, identification and measurement are also reviewed in this paper. Generally speaking, the chemical components of auxins in algae are indol acetic acid (IAA) and indol acetic acid-like substances. The distribution of auxins in algae varies with the species, growth stages, position in algae, and their forms. Bioassay systems are not specific enough to eliminate false positive results, and chemical identifications are far from conclusive because of their low concentration. Unambiguous and definitive identifications must be made by gas chromatography-mass spectrometry (GC-MS) and/or nuclear magnetic resonance (NMR).