两者意思一样.用法也有时一样.唯一的区别是whoever可以引导名词性从句而no matter who不能.如：
You can ask whoever is in charge of the company.无论是谁负责这家公司,你都可以问他/她.
这里的whoever is in charge of the company是宾语从句,whoever不能换成no matter who.
请看下面的两个例子：
Whoever is in charge of the company,you can ask him/her.
= No matter who is in charge of the company,you can ask him/her.
这两句都是引导让步状语从句,且与主句有逗号隔开.
注意：
（1）与whoever一样,whatever,whomever,whichever这几个疑问代词不仅可以引导名词性从句,也可引导让步状语从句.引导让步状语从句时等于no matter what,no matte whom,no matter which.
（2）whenever,wherever,whyever,however是疑问副词,不能引导名词性从句.所以它们与no matter when,no matter where,no matter why,no matter how的用法完全相同,都只能引导让步状语从句.
