1.意思上的区别
keep doing的意思是：保持，一直不间断地做某事。keep doing 是持续干某事。
keep to do 的意思是：保持，坚持；继续去做。to 是介词。keep to do 是保持干某事的某种状态。
2.用法上的区别
keep doing表示继续做某件事,重复做某事,指前面做过的事情或者刚刚在做的事情。
keep to do表示继续做另一件事情,是指与前面刚做的事情是不同的。
3.例句
keep doing
1.Just keep doing the one-on-ones, as they will produce more and make you look interested.
继续进行一对一的讨论就好了，因为这种讨论成果更为丰厚，也会让你看上去对这个问题是感兴趣的。
2.Would you keep doing what you do now if money would not be an issue?
如果钱不是问题的话，你还会继续做你现在做的事情吗？
3.I can keep doing push-up for one hundred times everyday.
我能每天坚持做俯卧撑一次，每次一口气100个。
4.if they do enjoy it less, why do they keep doing it?
既然乐趣少了，她们为什么还继续这么做呢？
5.That's a real motivator to keep doing what we're doing.
那是一直做我们正做的的真正的操纵机构。
keep to do
1.But I must kill him and keep strong to do it.
可是我不得不把它弄死，我得保持精力来这样做。
2.You're obligated to keep trying to do the best you can every day.
你没有义务去赢，但你有义务每天全力以赴！
3.Why do you keep trying to do that?
你干吗一直想那么做？
4.Don't keep asking me what to do; use your own discretion.
不要老是问我该做什么事，你自行决定吧。
5.Keep busy in order to do good job. Don't keep busy for nothing.
忙是为了把事干好，事没干好，忙将失去意义！