Provided is a speed controller hydraulic slave system median self-diagnosis self-positioning self-adaptive method. The method comprises: a speed controller electrical control system acquiring main distribution position feedback M, main distribution position set Mset and other data; detecting whether a speed controller hydraulic slave system is in a static balance, criterion including main distribution position set Mset being constant, if the criterion being satisfied, performing speed controller proportional valve median self-diagnosis, if not, waiting the criterion condition to be satisfied;performing speed controller proportional valve median drifting self-diagnosis, criterion including the main distribution position feedback M not being equal to the main distribution position set Mset;if M=Mset, setting of a proportional valve median set value B0 being rational, the proportional valve median set value B0 being equal to a proportional valve actual median value B0actual, entering amain distribution electrical median diagnosis step; if M is not equal to Mset, median of a proportional valve drifting, and setting of the proportional valve median set value B0 being not rational, performing proportional valve electrical median positioning correction. The method solves problems that a speed controller hydraulic slave system frequently adjusts and guide vane opening cannot be adjusted in place and other adjusting quality caused by drifting of the speed controller main distribution and the proportional valve electrical median, so as to adapt to current operating working conditions.