A rotary drill and a double-layer drilling rod mechanism are disclosed. A connecting rod (2) is provided in the rotary connecting sleeve (9), and the rotary connecting sleeve (9) is connected with the double-layer drilling rod mechanism (11). An impact drilling string (25) located by a guide bearing bush (26) is arranged in the outer rotary drilling pipe (28) of the double-layer drilling rod mechanism (11); a latch (24) for connecting the connecting rod (2) is arranged at the top of the inner impact drilling string (25); and an impact head (12) connected with the impact drilling string (25) is arranged in the drilling bit connecting sleeve (29). The drilling bit (13) below the impact head (12) is connected with the drilling bit connecting sleeve (29) by a front connector (30).