The invention relates to flame-retardant yarn made by sulfonyl-containing aromatic polymer fibers and high-temperature-resistant flame-retardant fibers, fabric and clothes made by the yarn and preparation methods of the flame-retardant yarn, the fabric and the clothes. The flame-retardant yarn comprises the sulfonyl-containing aromatic polymer fibers (A) and high-temperature-resistant flame-retardant fibers (B), the sulfonyl-containing aromatic polymer fibers (A) are made by sulfonyl-containing aromatic polymer which is formed by polymerizing the following three monomer: meta-position diamine-containing aromatic monomer (a), monomer (b) containing sulfonyl and amino and a para-position aromatic monomer containing dicarboxylic acid base group or halogen compound (c), and mass percentage of sulfonyl in the polymer is 4-10% in the sulfonly-containing aromatic polymer. The sulfonly-containing aromatic polymer fibers and other high-temperature-resistant flame-retardant fibers are blended for use, so that comfortability of the fabric and the clothes can be enhanced, and higher flame-retardant thermal protection performance can be maintained or improved.