The disclosure provides an operation adjustment method and system for metro trains under train out of service. The method includes: acquiring basic parameters of a metro system, information of the train out of service and the online normal running trains, determining follow-up train services and current train timetables thereof, adjusting the current timetables according to predicted time to stop service of the train out of service to obtain initial adjusted train timetables, determining canceled planned train services and rolling stocks for executing remaining planned train services, and adjusting the initial adjusted train timetables according to planned train timetables of the cancelled planned train services. The disclosure can automatically adjust the train operation, and reasonably change the train timetables and the rolling stock circulation plan, thereby reducing influences of the train out of service, and improving the degree of automation of the metro system to adapt to refined management.