Waste fried oil was studied to prepare three different types of detergent such as soap, liquid soap and soap powder via saponification process. The preparation conditions of soap base were optimized by orthogonal experiment. The specific preparation processes included waste fried oil treatment, orange peel extract preparation, saponification, demoulding and drying. Results showed that the optimal conditions for saponification were as follows: ratio of pure waste fried oil to coconut oil = 6:4, alkali liquor (NaOH) mass fraction 30%, saponification temperature 70 °C, orange peel extract concentration 15%. The mature soap was then used to make liquid soap and soap powder by surfactant (sodium dodecylbenzene sulfonate, coconut diethanol amide) addition, followed by grinding. The prepared detergent conforms to the production standard of strong decontamination ability, possesses stable performance, is gentle to skin and non-toxic.