A circular rapid-joint connector, including: a sliding bush (1, 1a); an elastic element provided on the inner edge of the sliding bush (1, 1a); a holding unit (3, 3a) joined with the sliding bush (1, 1a) movably; and a connector plug penetrating into the sliding bush (1, 1a) and joined with the holding unit (3, 3a); wherein an end of the connector plug forms a top portion, and wherein the connector plug is provided with multiple insertion terminals therein, while one side of the top portion is provided with an annular plate, wherein the top portion is further provided with a ditch thereon annularly, characterized in that the other end of the connector plug forming a second external thread portion; a containing area (11, 11a) capable of accommodating the elastic element is provided on the inner edge of the sliding bush (1, 1a), wherein an end of the sliding bush (1, 1a) has multiple buckle holes (12, 12a) engaged with the holding unit (3, 3a), and wherein the inner edge of another end of the sliding bush (1, 1a) has a stop portion (13, 13a) abutting against the annular plate of the connector plug; the holding unit (3, 3a) comprises a sleeve (31, 31a), a collar (32, 32a) provided in the sleeve (31, 3 1a), and a locking bush (33, 33a) joined with the sleeve (31, 31a), wherein the outer edge of the sleeve (31, 31a) has multiple buckles (311, 311a) docking with the buckle holes (12, 12a) of the sliding bush (1, 1a) respectively, and an end of the sleeve (31, 31a) has multiple adjacent elastic pieces (312, 312a), the inner surface of each of the elastic pieces being provided with a respective sticking point, while the periphery of the collar is provided with a slot docking with each of the sticking points, and the inner edge of the sleeve (31, 31 a) is provided with a first internal thread portion (314, 314a) joined with the second external thread portion of the connector plug, and wherein a first external thread portion (315, 315a) is provided on the outer edge of the sleeve (31, 31a) where each of the elastic pieces (312, 312a) is adjacent thereto, while the inner edge of the locking bush (33, 33a) is provided with a second internal thread portion (331, 331a) joined with the first external thread portion (315, 315a), and the buckle holes (12, 12a) of the sliding bush (1, 1a) are larger than the buckles (311, 31 1a) of the sleeve (3 1, 31a), and wherein the top portion is further provided with a marking portion thereon, and the connector plug is provided with a guiding portion therein. a sliding bush (1, 1a); an elastic element provided on the inner edge of the sliding bush (1, 1a); a holding unit (3, 3a) joined with the sliding bush (1, 1a) movably; and a connector plug penetrating into the sliding bush (1, 1a) and joined with the holding unit (3, 3a); wherein an end of the connector plug forms a top portion, and wherein the connector plug is provided with multiple insertion terminals therein, while one side of the top portion is provided with an annular plate, wherein the top portion is further provided with a ditch thereon annularly, characterized in that the other end of the connector plug forming a second external thread portion; a containing area (11, 11a) capable of accommodating the elastic element is provided on the inner edge of the sliding bush (1, 1a), wherein an end of the sliding bush (1, 1a) has multiple buckle holes (12, 12a) engaged with the holding unit (3, 3a), and wherein the inner edge of another end of the sliding bush (1, 1a) has a stop portion (13, 13a) abutting against the annular plate of the connector plug; the holding unit (3, 3a) comprises a sleeve (31, 31a), a collar (32, 32a) provided in the sleeve (31, 3 1a), and a locking bush (33, 33a) joined with the sleeve (31, 31a), wherein the outer edge of the sleeve (31, 31a) has multiple buckles (311, 311a) docking with the buckle holes (12, 12a) of the sliding bush (1, 1a) respectively, and an end of the sleeve (31, 31a) has multiple adjacent elastic pieces (312, 312a), the inner surface of each of the elastic pieces being provided with a respective sticking point, while the periphery of the collar is provided with a slot docking with each of the sticking points, and the inner edge of the sleeve (31, 31 a) is provided with a first internal thread portion (314, 314a) joined with the second external thread portion of the connector plug, and wherein a first external thread portion (315, 315a) is provided on the outer edge of the sleeve (31, 31a) where each of the elastic pieces (312, 312a) is adjacent thereto, while the inner edge of the locking bush (33, 33a) is provided with a second internal thread portion (331, 331a) joined with the first external thread portion (315, 315a), and the buckle holes (12, 12a) of the sliding bush (1, 1a) are larger than the buckles (311, 31 1a) of the sleeve (3 1, 31a), and wherein the top portion is further provided with a marking portion thereon, and the connector plug is provided with a guiding portion therein.