1.查看"维护计划"对象的ID
use msdb
select * from sysmaintplan_plans
select * from sysmaintplan_log
select * from sysmaintplan_subplans
2.根据ID号删除相应的"维护计划"
delete from sysmaintplan_log where plan_id = ''
delete from sysmaintplan_subplans where subplan_id = ''
delete from sysmaintplan_plans where id = ''