Microelectrodes for in situ chemical measurements in sediments are powerful techniques that cannot be substituted by alternative methods and are receiving increasing attentions from scientific community. This paper introduces three major electrochemical categories of microelectrodes that have practical applications in quantifying sediment chemistry, and cover the working principles, construction procedures, and applications of pH microelectrode, pCO₂ microelectrode, sulfide selective microelectrode, oxygen membrane microelectrode, and Hg-Au voltammetric microelectrode in sediments. In particular, this paper describes the electrochemical properties of Iridium oxides pH microelectrodes and Hg-Au microelectrodes constructed in the laboratory and provides in details technicalities for measuring redox chemical species in sediments by voltammetry. It is believed that microelectrode applications have deepened biogeochemical study in sediments.