The invention provides a method for preparing nonoxynol without ethylene oxide. The method comprises the following steps that a, nonyl phenol and alkali which are taken as raw materials are added intoa reaction still, and air is replaced with nitrogen; b, the temperature rises, and ethylene oxide is introduced; c, after introducing is finished, a sample is taken for detecting cloud points, afterthe cloud points are qualified, alkali is supplemented, and the reaction continues for some time; d, the reaction stops, and the temperature is reduced; e, a sodium chloride aqueous solution is adopted for washing; f, vacuum drying is conducted; the nonoxynol is shown in the formula I. According to the method, after finishing of the reaction, sodium hydroxide is supplemented, ethylene oxide remaining in reaction liquid can be completely consumed, finally, the obtained nonoxynol crude drug does not contain the ethylene oxide, and the quality of the nonoxynol crude drug is improved. In the reaction process, the content of the ethylene oxide is reduced, the frequency of washing in the after-treatment process can be reduced, discharged waste water is reduced, and the method is green and environmentally friendly. The method is short in reaction steps and simple in operation, industrial scale-up production is convenient, and the nonoxynol without ethylene oxide can be obtained.