A draft of the law has been submitted to the Legislative Assembly, state media reports.
According to the draft, Hong Kong's government and judiciary will effectively try to prevent, stop and punish activities that threaten national security.
The Taiwan government urges Beijing not to cause major concern in Hong Kong by making wrong decisions.
"Consequences for Hong Kong's relative independence"The Chinese action is a restructuring of the previous course, which has been based on allowing the Hong Kong Legislative Assembly itself to decide when and how the disputed 23rd article in the Hong Kong Constitution should be put into practice. Article 23 states that Hong Kong must introduce national security legislation prohibiting, for example, treason and incitement, but not when or how.
The plans could have far-reaching consequences for Hong Kong's relative independence, according to experts.
The United States has previously warned of strong condemnations if the proposal is introduced.