The invention relates to the technical field of softening agents, in particular to a ternary polymerization block polyether amino silicon oil softening agent. The structural formula is shown in the description, wherein R=-CH2CH2CH2, -CH3 or -CH2CH3, R'=C1-22 alkane, PO=OC3H6, EO=OC2H4, a and b are any integer from 5 to 24, c is any integer from 10 to 60, and n is any integer from 10 to 60. Yellowing, instability and hydrophobicity of ordinary amino silicon oil are overcome, fabric has excellent hand feeling, hydrophilia, washability and stability, and the softening agent is suitable for various kinds of pure cotton fabric, cotton-polyester blended fabric, wool and other kinds of fabric.