According to a draft of revisions to the proposed law, a wide range of behaviour, including dress or speech “detrimental to the spirit of the Chinese people and hurt the feelings of the Chinese people" would be prohibited.
The draft was released by the standing committee of the nation's legislature and has been listed among their priorities for passage this year, Bloomberg reported.
Violating the law would send a person to a detention centre for up to 15 days or hand over a fine of up to 5,000 yuan (£545). However, it was unclear what images or speech would be considered offensive by the government.
The draft law highlights president Xi Jinping's bid to throttle dissent in the nation of some 1.4 billion people over his decade in power.
A woman was detained last year in Suzhou, a city near Shanghai, for wearing a kimono (a traditional Japanese attire) in public, according to the report.
Chinese authorities in recent months have clamped down on people wearing shirts with rainbows at concerts or distributing flags with pro-LGBTQ+ symbols on them.
The proposed law has led to outrage among Chinese citizens on social media, with people questioning how the authorities would know when the nation's feelings would be hurt.
“Shouldn’t the spirit of Chinese nation be strong and resilient,” Weibo handle “Nalan lang yueyueyue” asked. “Why can it be easily damaged by a costume?”
Earlier in 2019 during the pro-democracy protests in Hong Kong, the Chinese government had placed a ban on exports of black clothes from the mainland to the financial hub.
Protesters had adopted plain black T-shirts, trousers and face masks as their uniform during rallies.
Black shirts and other clothing, helmets, umbrellas, walkie-talkies, drones, goggles and metal chains were among the items banned by Beijing.