The invention relates to the field of water reducers, in particular to novel application of a compound capable of serving as a water reducer (namely capable of partially replacing a polycarboxylic acid water reducer). The invention provides application of a compound or salt serving as a water reducer. The structural formula of the compound is A-Ba or A-R-Ba, wherein A is selected from anion groups; B is selected from hydrophilic groups. The compound is simple in chemical structure and clear in action principle, thereby being easy to select.