The invention, which belongs to the technical field of the textile machinery, relates to an automatic yarn adjusting and feeding apparatus of a circular knitting machine. With the apparatus, a problem that yarn adjustment can not be realized according to the existing dual-surface circular knitting machine in the prior art can be solved. The apparatus comprises a yarn adjustment mechanism arranged at a knitting mechanism of the circular knitting machine. The yarn adjustment mechanism includes a yarn adjustment support and a shuttle support arranged at the yarn adjustment support; a first shuttle and a second shuttle are hinged to the shuttle support and yarns with different colors can penetrate the first shuttle and the second shuttle; and a drive mechanism for driving the first shuttle and the second shuttle to be stretched or retracted is arranged at the shuttle support. Besides, a yarn cutting mechanism for cutting off and clamping yarns at the first shuttle or the second shuttle is also arranged at the side of the yarn adjustment support. According to the apparatus, because of the yarn adjustment mechanism and the cutting and clamping mechanism, yarn adjustment of the circular knitting machine becomes simple and convenient; and automatic yarn adjustment can be realized. The color expression effect of the knitted fabric is substantially optimized.