The invention relates to an autoleveling system with cotton sliver weight control and a weight control method thereof. The autoleveling system comprises a cotton-feeding roller mechanism, a coiler, a cotton sliver bucket, an autoleveling device, a cotton layer thickness detection sensor and / or a cotton sliver thickness detection sensor, and a weight sensor for weighting a cotton sliver in the cotton sliver bucket, wherein the output end of the weight sensor is connected with the autoleveling device for controlling the output speed of the cotton-feeding roller mechanism; the weight sensor comprises a strain foil and a weight amplifier, and the strain foil is a bridge resistor circuit. The autoleveling system detects the weight of the cotton sliver after a certain length of cotton sliver is continuously produced, and the autoleveling device compares a detected weight with a standard weight stored in a program and controls the output speed of the cotton-feeding roller mechanism according to a comparison result. The invention realizes the online weight detection of an overlength section of cotton sliver, can effectively correct the weight deviation of the overlength section of cotton sliver in time, lightens the labor intensity of an operator and improves the detection precision.