The most effective way to detect a fake Chinese money is the watermark. Hold the bill up against light, a watermark of Chairman Mao is shown. The watermark on a real 100 Yuan banknote is distinct while the watermark on a fake one is rather obscure. Look at watermarks in the blue boxes which I draw in the follow pictures and compare.
Watermark on a real 100 Yuan banknote (In the blue box and click the enlarge)