In the fuzzy information system, tolerance relation of the λ level sets based on the similar degree of the objects can be obtained by the ordered weighted averaging (OWA) operator. Indiscernibility relation and grain size are affected by the fuzzy quantifier parameters (α,β) of the OWA operators, when the value of λ is the same. Therefore, it is worth to study how to reasonably select fuzzy quantifier parameter (α,β) values. Parameter selection of OWA operators is discussed based on three-way decisions of rough set theory in fuzzy information system. According to radicalness, mean, and negative of parameters semantics, three most commonly used values of (α,β) are proposed. Furthermore, related properties of similar degrees, tolerance classes, upper and lower approximation sets as well as three-way regions are discussed based on three most commonly used values of (α,β). Finally, experimental results are used to analyze reasonableness of semantic explanations about fuzzy quantifier parameters. The study adopts a novel viewpoint of three-way decisions theory, and the new semantic explanations and validity of selection methods about related fuzzy quantifier parameters (α,β) in the OWA operators are given in fuzzy information system.