我的情况是这样的，最近接受了公司外派回国的机会，但是我还在opt中，以为以后没法归海了
昨天HR的人说外派的话也可以办绿卡，而且公司愿意给我办，不知道真的假的哦

我这个职位title很高，但是pay没有特别多，而且中国只是设立了办事处，这样可以申请L1的签证然后申请EB1-C么？

yes you can. You can apply for EB-1 "executive of multinational company" without have to go through L-1 (of course you can do that, but L-1) is not a pre-request for EB-1. The company will need to justify that your position is an "executive" one rather than manager. They will ask specifically on your job describtion, sometimes JD of your boss and JD of the people you're managed.
The only difficulty will be to build a strong case for "Executive position" if your company is not a very big one and there are not a lot of people under you in China office.