Abstract: By taking CTD and LADCP observations as the examples, the status of self-winding/knotting of coaxial armored cable in the downward marine observations is analyzed and studied from the aspects of sea conditions during work, underwater unit structures and their underwater attitudes. It can be found that the frame of the observation instrument can rotate during its downward release and the torsion generated by the rotation can act on the coaxial armored cable. If the torsion cannot be released, the coaxial armored cable will easily be lead to self-winding/knotting in poor sea conditions. For solving this problem, a set of practical improvement solutions is put forward, that is, under the premise of working both in poor sea conditions and without reducing the observation instruments the connection structure between the frame of observation instrument and the coaxial armored cable should be improved and the mechanical swivel ring and auxiliary structures should be added. It has been proved that this set of solutions can effectively avoid the "knotting" phenomenon caused by self-winding of coaxial armored cable in ocean observations similar to the CTD/LADCP. This solution can not only improve greatly the efficiency of field observations, but also ensure the safety of the instrument and the transmission of data. This technology is derived from basic ocean observation practices and can provide a useful reference for the vast majority of ocean investigators.