How do I find the missing record in my chinese genealogy record?

I have found my chinese genealogy record which allow me to trace many generations of ancestors back to Han Dynasty, however, the record are not complete and many record are still missing when I try to trace the record back to older times. I wonder how can I find the missing record so continue my family history work?

我找到了我的族谱，可以追溯到汉代很多代的祖先，但是这份族谱并不完整，当我尝试追溯更久远的时期时，仍然有很多记录缺失。我想知道如何才能找到缺失的记录，以便继续我的家族史研究？