I'm married to a China wife in Singapore request for long stay in China

You can stay in China for a long time. You can try to apply for a Q1 to stay in China for at least more than 180 days.

To apply Q1, you need to prepare your valid passport, an application form with a recent taken photo, an invitation letter from your Chinese wife, her Chinese ID card and your marriage certificate. After get the Q1, you need to change it to a resident permit within 30 days of your arrival. Then you can stay in China for a long time.