Girlfriends are often harassed or even threatened by phone calls and text messages from ex-boyfriends. How should I sue him?

Collect evidence first and keep or record his threats.

If the evidence is conclusive, he can be prosecuted in the public security organ and asked to be punished by the public security organ.

It can be punished according to Article 42 of the Law on Public Security Administration Punishment: anyone who commits one of the following acts shall be detained for not more than five days or fined not more than five hundred yuan; If the circumstances are serious, they shall be detained for more than five days and less than ten days, and may be fined up to five hundred yuan:

Writing threatening letters or threatening the personal safety of others by other means.