The present invention provides a fine-long animal hair fibre and its production method which can fix its stretched state, do not damage crimp recovery, reduce fibre diameter, increase fibre length and raise fibre glossiness. Its production includes the following steps: (a) for animal hair stripe, implementing twisting procedure; (b) soaking the twisted animal hair stripe in alkaline aqueous solution and making the animal hair stripe undergo the process of swelling and plasticity treatment; (c) reduction procedure for cutting disulfide bond in the swelling plasticity fibre; (d) drawing procedure for actually drawing the swelling plasticity fibre to 1.20-1.60 times; (e) using oxidant to oxidate the drawn animal hair fibre; and (f). using acid to make neutralization.