The invention provides an environmentally-friendly 
Setaria viridis 
softening agent preparation method, which comprises: washing 
Setaria viridis, 
drying, crushing, and screening; adding 
petroleum ether, and extracting; filtering, and distilling to remove the 
petroleum ether to obtain an extract A and filtering residue; adding the extract A to a NaOH solution in a dropwise manner, and carrying out areaction; cooling, adding 
hydrochloric acid in a dropwise manner, carrying out 
thermal insulation, carrying out standing layering, taking the upper layer liquid, washing, and carrying out rotary 
evaporation to obtain a component B; carrying out a stirring heating reaction on the component B, 
stannous oxide and 
oxalyl chloride; carrying out cooling pressure reducing 
thermal insulation, and coolingto obtain a component C; taking the filtering residue, adding an 
ethanol aqueous solution, and carrying out water bath heating 
reflux; filtering to obtain an extraction liquid, carrying out adsorption decoloration, and carrying out pressure reducing 
distillation to obtain a component D; and mixing and stirring the component C and the component D to obtain the product. According to the present invention, the prepared environmentally-friendly 
Setaria viridis 
softening agent has good softness to the cloth, does not irritate to the 
skin, and further has characteristics of soft hand feeling, strong smoothness, good wettability and good 
softening effect.