A rotor spinning method for two-sliver asynchronous inputting and three-level carding, comprising: 1) feeding fiber by a combined feeding roller comprising two feeding rollers (2-1, 2-2) with two rotational freedom degrees into carding area where a three-level carding roller comprising three carding rollers (2-6, 2-7, 2-8) is used for carding; 2) moving the two feeding rollers (2-1, 2-2) at linear speeds V 01 and V 02, respectively; moving a rotor at a linear speed V 4 and moving a guide roller at a linear speed V 5; setting linear densities of two slivers (2-3, 2-4) drafted by the two feeding rollers (2-1, 2-2) to be ρ 1 and ρ 2, respectively, and setting a rotor spun yarn density to be p, such that a draft ratio of a rotor spinning yarn is as below: E = ρ 1 + ρ 2 V 5 ρ 1 V 01 + ρ 2 V 02 = ρ 1 + ρ 2 ρ a linear density of the rotor spun yarn is formed, ρ= ρ 1 V 01 + ρ 2 V 02 V 5 wherein speeds of the three carding rollers (2-6, 2-7, 2-8) are as follows: a speed of a first carding roller is 1500-3000 rpm, a speed of a second carding roller is 3000-6000 rpm, a speed of a third carding roller is 6000-12000 rpm, 3) blending ratios of the two slivers (2-3, 2-4) in the rotor spinning yarn are K1 and K2 respectively: K 1 = ρ 1 V 01 ρ 1 V 01 + ρ 2 V 02 K 2 = ρ 2 V 02 ρ 1 V 01 + ρ 2 V 02 4) assuming that the speed V 5 of the guide roller is invariable, the variables of feeding speeds V 01 and V 02 of the two feeding rollers (2-1, 2-2) of the two slivers (2-3, 2-4) are respectively as follows: V 01 ' = V 01 + ΔV 01, V 02 ' = V 02 + ΔV 02, then the dynamic linear density of the rotor spun yarn is obtained according to formula Δρ= ρ 1 Δ V 01 + ρ 2 Δ V 02 V 5 5) assuming that ρ 1 = ρ 2 = ρ 0, V 01 +V 02 = V 0, obtaining a reference blending ratio according to the formulas, as K 1 = V 01 V 0, K 2 = V 02 V 0, wherein, when V 01 +V 02 →V 01 +ΔV 01 +V 02 +ΔV 02, the blending ratio becomes as below: K 1 ′ = V 01 + Δ V 01 V 0 + Δ V 0 K 2 ′ = V 02 + Δ V 02 V 0 + Δ V 0 realizing dynamically adjustable spinning of different color blending ratios or color mixing ratios in the yarn with different fibers or colors by controlling of V 01 and V 02. 1) feeding fiber by a combined feeding roller comprising two feeding rollers (2-1, 2-2) with two rotational freedom degrees into carding area where a three-level carding roller comprising three carding rollers (2-6, 2-7, 2-8) is used for carding; 2) moving the two feeding rollers (2-1, 2-2) at linear speeds V 01 and V 02, respectively; moving a rotor at a linear speed V 4 and moving a guide roller at a linear speed V 5; setting linear densities of two slivers (2-3, 2-4) drafted by the two feeding rollers (2-1, 2-2) to be ρ 1 and ρ 2, respectively, and setting a rotor spun yarn density to be p, such that a draft ratio of a rotor spinning yarn is as below: E = ρ 1 + ρ 2 V 5 ρ 1 V 01 + ρ 2 V 02 = ρ 1 + ρ 2 ρ a linear density of the rotor spun yarn is formed, ρ= ρ 1 V 01 + ρ 2 V 02 V 5 wherein speeds of the three carding rollers (2-6, 2-7, 2-8) are as follows: a speed of a first carding roller is 1500-3000 rpm, a speed of a second carding roller is 3000-6000 rpm, a speed of a third carding roller is 6000-12000 rpm, 3) blending ratios of the two slivers (2-3, 2-4) in the rotor spinning yarn are K1 and K2 respectively: K 1 = ρ 1 V 01 ρ 1 V 01 + ρ 2 V 02 K 2 = ρ 2 V 02 ρ 1 V 01 + ρ 2 V 02 4) assuming that the speed V 5 of the guide roller is invariable, the variables of feeding speeds V 01 and V 02 of the two feeding rollers (2-1, 2-2) of the two slivers (2-3, 2-4) are respectively as follows: V 01 ' = V 01 + ΔV 01, V 02 ' = V 02 + ΔV 02, then the dynamic linear density of the rotor spun yarn is obtained according to formula Δρ= ρ 1 Δ V 01 + ρ 2 Δ V 02 V 5 5) assuming that ρ 1 = ρ 2 = ρ 0, V 01 +V 02 = V 0, obtaining a reference blending ratio according to the formulas, as K 1 = V 01 V 0, K 2 = V 02 V 0, wherein, when V 01 +V 02 →V 01 +ΔV 01 +V 02 +ΔV 02, the blending ratio becomes as below: K 1 ′ = V 01 + Δ V 01 V 0 + Δ V 0 K 2 ′ = V 02 + Δ V 02 V 0 + Δ V 0 realizing dynamically adjustable spinning of different color blending ratios or color mixing ratios in the yarn with different fibers or colors by controlling of V 01 and V 02.