as soon as

as soon as
一……就……
I'll write you as soon as I get there.
我一到那儿，就给你写信。
Let us start as soon as he comes.
等他一来我们就动身。
I gave the alarm as soon as I saw the smoke.
我一看见冒烟，就发出了警报。
As soon as his father went out, the boy ran to the cinema.
爸爸刚出门，那男孩就跑向电影院。
I arranged the flowers in the vase as soon as I came back home.
一回到家里，我就把花在花瓶里插好。
They will post the tickets to me as soon as they receive my cheque.
他们收到我的支票后就立刻把票寄给我。

详解：

once 和as soon as 两者均为从属连词，引导时间状语从句，都表示主句的动作紧跟在从句的动作之后发生。
once除表时间外，还表示条件，一般译作“一旦......就......”。
他一旦下定决心，就决不会放弃（本句不可用as soon as）。
Once he makes up his mind，he’ll never give it up.
as soon as强调的只是时间，译作“刚......就......”或“一......就......”。
我一到北京就写信给你。
As soon as I get to Beijing，I’ll write to you.

as...as<-->as far as