Is SMS threat illegal?

SMS threats are illegal. Coercion must be illegal. Coercion is coercion and threat to another party, which must be illegal. If one party has a legitimate basis to exert some pressure on the other party, it does not constitute coercion. If, after the conclusion of the contract, one party refuses to perform its contractual obligations, and the other party puts pressure on the other party to perform the contract by legal means such as filing a lawsuit, it does not constitute coercion. The harm claimed by the coerced person must be that the coerced person can believe what will happen and it is enough to make the coerced person feel terror and fear.

People's Republic of China (PRC) Public Security Administration Punishment Law

Article 42

One of the following acts shall be detained for less than 5 days or fined for less than 500 yuan; If the circumstances are serious, he shall be detained for more than 5 days 10 days, and may also be fined up to 500 yuan:

(1) writing threatening letters or threatening the personal safety of others by other means;

(2) publicly insulting others or fabricating facts to slander others;

(3) fabricating facts, falsely accusing and framing others, and attempting to subject others to criminal investigation or public security administration punishment;

(4) Threatening, insulting, beating or retaliating against witnesses and their close relatives;

(5) sending obscene, insulting, intimidating or other information for many times to interfere with the normal life of others;

(six) voyeurism, sneak shots, eavesdropping, spreading the privacy of others.