The UI language of Jenkins and SonarQube (previously Sonar) is determined by two things: 1. If your Jenkins/SonarQube server has locale plugin; 2. your browser language settings.
Locale Plugin
Install Jenkins Locale Plugin or SonarQube Chinese Pack. Then your server has multilingual ability.
Browser Language Settings
In Chrome, it is [Settings -> Advanced Settings -> Languages -> Languages and spell-checker settings], drag "English" upper than "Chinese".