Abstract: In order to explore the best test conditions for the removal of heavy metal cadmium by fly ash,the fly ash dosage, adsorption pH value, adsorption time, adsorption temperature as factors, it makes the adsorption amount of cadmium in wastewater as the test object. The results show that when the dosage of fly ash is 1.5 g, the pH value of waste water is 4, and the temperature is 30℃, the removal rate of cadmium in waste water can reach 82.39%.