Abstract: Effects of ammonium ion content in fly ash on the fluidity of fresh concrete, the superplasticizer dosage in concrete and the properties of concrete were studied, and the effect of adsorption on superplasticizer was analyzed by TOC test. Results show that as the content of ammonium ion in fly ash increases, the fluidity of fresh concrete decreases. When maintaining the close fluidity, as the content of ammonium ion in fly ash increases, the superplasticizer dosage in concrete increases, and the strength of concrete decreases. TOC test shows that the higher content of ammonium ion is, the greater adsorption of superplasticizer will be.