strait-laced       
adjective  disapproving uk/ˌstreɪtˈleɪst/ us/ˈstreɪt.leɪst/
 (尤指在性问题上)古板的,拘谨的,保守的
having old-fashioned and unchanging morals, especially relating to sexual matters
  The joke shocked her strait-laced parents. 这个笑话让她古板的父母惊呆了。 
 Synonyms: priggish prim prissy puritanical