He is a lucky dog. 他是个幸运儿。

 lead a dog's life 过穷困潦倒的日子 (来源：英语交友 http://friends.englishcn.com)

 not have a dog's chance 毫无机会

 top dog 当权派；头儿

 treat sb. like a dog 不把某人当人看

 a hunting dog 猎犬

 a lazy dog 懒汉

 a gay dog 一个快乐的人

 a dirty dog 下流坯

 dog-days n.[pl.]三伏天, 大热天; 无所作为的时期, 无精打彩的日子

 A good dog deserves a good bone.
[谚]好狗应该啃好骨头, 有功者受赏。

 A living dog is better than a dead lion.
[谚]死狮不如活狗。

 A staff [stick] is quickly [soon] found to beat a dog with.
[谚]欲加之罪, 何患无辞。

 An old dog barks not in vain.
[谚]老狗不乱吠; 老狗 一吠, 就得小心。

 An old dog will learn no new tricks. (=You cannot teach old dogs new tricks.)
[谚]老狗学不了新把戏; 老年人很难适应新事物。

 as [like] a dog with two tails
非常开心[高兴]

 Barking dogs seldom bite.
[谚]爱叫的狗 不咬人; 咬人的狗不露齿。

 be (old) dog at (a thing)
对...有经验; 对...很内行

 Beware of a silent dog and still water.
[谚]提防不吠的狗, 小心 静止的水。

 come like a dog at a whistle
一呼即来

 Every dog has his day.
[谚]凡人皆有得意日。

 Every dog is a lion at home. [Every dog is valiant at his own door.]
[谚]狗是百步王, 只在门前凶。

 Fight dog, fight bear.
[谚]打个青红皂白, 一决雌雄。

 Give a dog a bad [an ill] name(and hang him).
[谚]一旦给人加一个坏名声, 他就永远洗刷不掉; 人言可畏。

 It is ill to waken sleeping dogs. [let sleeping dogs lie; don't wake a sleeping dog.]
别多事, 别惹麻烦。

 lead a dog's life
过着牛马不如的生活

 love me, love my dog.
[谚]你若把我当朋友, 也要把我的朋友当朋友; 爱屋及乌。

 Scornful[Hungry] dogs will eat dirty puddings.
[谚]人到危急时, 平时所不屑做的也要做; 急不暇择, 饥不择食。

 teach an old dog new tricks
使守旧的人接受新事物

 teach the dog to bark
教狗怎么叫(意指多此一举)

 The dog returns to his vomit.
狗回头吃自己吐出来的东西; 重犯旧日罪恶。