China has two rivers, the Yellow and the Yangtze, which stretch from sea in the east and then travel hundreds of miles inland. The river valleys that surround these rivers account for nearly 2/3 of the current Chinese land mass. This gave early Chinese governments the advantage of being able easily control their territory just by controlling these two rivers. Contrast this with the geography of Europe. Yes there are large rivers in Europe, but no single or two river stretch across Europe. You would need to have control over nearly a dozen rivers to have the same easy of movement and control over you Europe that you can have over the China. This made early Chinese governments and their bureaucracies far more effective than there European counterparts.
Secondly, you have a lack of large mountain ranges. In Europe the Alps, Pyrenees, Carpathians, and Dinaric Mountain crisscross all of Europe. China lacks these natural barriers, and like the rivers, this makes China more easily controlled from a single central location.
Together, the two large rivers, and lack of large mountains made China a more hospitable area for centralized governments. Perhaps the biggest effect was the establishment and growth of the Chinese bureaucratic class and the testing system that developed them. By having a need for bureaucrats to help run this large area, China developed class that wouldn't take in Europe till centuries later.