MySQL : Cannot add or update a child row: a foreign key constraint fails

Hello,

I Got MySql Error : Cannot add or update a child row: a foreign key constraint fails

This is my Insert Query :

Code:

INSERT INTO `swat` (`Category`, `Importance_JK`, `MaxStrength`, `Person_id`, `SWAT_id`, `Strength`, `cost`, `date_Complete`, `due_Date`, `storage_id`, `updated`, `user_FK`)
   VALUES ('1','2','we1','546','46','we','500','2016-04-19','2016-04-18','','2016-04-18','37')

If i print this query in SQL, then this MySql error occurs:

#1452 - Cannot add or update a child row: a foreign key constraint fails (`sidemoin_crucialstuff`.`swat`, CONSTRAINT `swat_ibfk_3` FOREIGN KEY (`Person_id`) REFERENCES `key_people` (`Key_Person_ID`))

Any help please?