Four comb-like polycarboxylic acid type water-reducers, four types of cements, three soluble sulphates and two kinds of ultrafine mineral powders were used to examine the compatibility of cements with water-reducers. The dispersion behavior of cement pastes was analyzed by Zeta potential measurement or mini-slump test. Properties of concretes with water-reducers and ultrafine mineral powders were tested by measuring the slump or slump-loss of fresh concrete as time and the compre-(ssive) strength of hardened concrete at certain ages. It is shown that the structure and performance of water-reducers, composition and properties of cements, multiple-charged cations of electrolyte, and the contents of ultrafine mineral powders are the primary factors influencing the compatibility of polycarboxylic acid type water-reducer with cement.