请问这样的合同我怎么签？

看来你不是做HR的，要不不会提这问题，你可以要求把那30%的部分写在附件中，其实只要是按原来说好的发，一般都不会有太大的问题，可能加班工资会受点影响。但你不签，估计这份工作就没了。

i am agree with the comment on above. you need make sure you can get thoses 30%, which should be writing on the attachement of the lablor contract. the company only doesn't want to pay to your overtime base on your base salary. if you want to refuse to sign of the contact that means you have to go soon. it is very dangerous for your career development in this company.

其实现在很多企业都是这样签的，劳动合同上的薪酬和实际发放的不一致，一方面是为了应付ZF检查，另一方面在一些保险方面能少交一些，有的可能也是为以后劳动纠纷做准备。