The invention discloses an online adjustable target flow switch, which comprises a pipe barrel (1), a pipe barrel flange (10), a target sheet (2), a rotating supporting plate (20), a rotating supporting plate seat (22), a target rod (3), a sliding column (30), an internal magnetic steel block (31), a compressed spring (4), a compressed spring adjustment device (5), a shell (6), a microswitch (7), an external magnetic steel block (71), a transmission rod mechanism (8) and a wiring terminal (9), wherein the shell (6) is fixedly arranged on the pipe barrel (1) through a support and the pipe barrel (1) is made to be placed in a groove (60) opened in the end surface of the shell (6). The sealing performance is reliable; and when a flow alarming value needs to be set again, a pipeline valve does not need to be closed, and an alarming point can be directly adjusted in the field and set.