The invention provides raphnus sativus compound vegetable powder and a preparation method thereof. The preparation method comprises the following steps of firstly, cleaning raphnus sativus and sweet potatoes, performing dicing, and adding water for mashing so as to obtain mixed slurry; performing homogenate on the mixed slurry with a colloid mill, adding a sweetening agent, a sour agent, maltodextrin and beta-cyclodextrine for blending mixed liquor after homogenate, performing homogenizing treatment on the mixed slurry after being blended, drying the mixed slurry after being subjected to homogenizing treatment, and performing grinding for flour milling so as to prepare the raphnus sativus compound vegetable powder. The vegetable powder prepared by the method disclosed by the invention is free from any artificial color, light in carmine, stable in color, uniform in powder texture, fine, smooth, and free from any impurities, has unique fragrance of the raphnus sativus and the sweet potatoes, does not have pungent taste of radishes, accepted by consumers, is coordinative in fragrance, and moderate in taste and sugariness, has rich lysine, is balanced in nutrients and conforms to demands of current consumers.