什么是 AMM（自动做市商）？｜DeFi 基础

什么是 AMM（自动做市商）？What is an AMM (Automated Market Maker)?

⏱ 7 分钟7 min

学习目标：学完你能理解 AMM 用资金池加公式自动定价的原理，知道 x 乘 y 等于 k 是怎么回事，以及为什么买得越多价格越贵。Learning goal: after this lesson you'll understand how an AMM prices automatically using a liquidity pool plus a formula, what "x times y equals k" is about, and why the more you buy, the more expensive it gets.

大白话In plain wordsAMM 就像一台自动售货机，价格不由人喊，而是由「池子里还剩多少货」按公式算出来——货越少，价越贵。An AMM is like a vending machine: the price isn't quoted by a person but calculated by a formula from "how much stock is left in the pool" — the less stock, the higher the price.

AMM 是自动做市商（Automated Market Maker）。传统交易靠买卖双方挂单撮合，而 AMM 换了个思路：把两种代币放进一个资金池，价格由一条数学公式自动算出，不需要有人挂单等对手。AMM stands for Automated Market Maker. Traditional trading matches buyers and sellers via an order book, but an AMM takes a different approach: put two tokens into a liquidity pool, and the price is calculated automatically by a math formula — no one needs to post an order and wait for a counterparty.

最经典的公式是恒定乘积：x 乘 y 等于 k。x 和 y 是池里两种币的数量，k 保持不变。你拿走一部分 A 币，池里 A 变少、B 变多，公式就自动把 A 的价格抬上去。The most classic formula is the constant product: x times y equals k. Here x and y are the amounts of the two tokens in the pool, and k stays constant. When you take some token A out, A in the pool drops and B rises, so the formula automatically pushes A's price up.

这带来一个直觉规律：This leads to some intuitive rules:

买的量越大，价格被推得越高The larger your buy, the higher the price gets pushed
池子越大（钱越多），价格越稳、越抗冲击The bigger the pool (more money in it), the more stable and shock-resistant the price
价格随时随成交自动变化，不用人工调The price changes automatically with every trade — no manual adjustment

所以 AMM 的价格是「算」出来的，不是「喊」出来的。理解这一点，你就明白了为什么大额交易滑点大、为什么小池子价格容易被拉动——这都是公式在起作用。So an AMM's price is "calculated", not "quoted" by anyone. Once you get this, you understand why large trades have big slippage and why small pools have prices that are easily moved — it's all the formula at work.

案例Example一个池子里有 100 个 A 和 100 个 B，k 就是 10000。你想拿走一些 A，池里 A 减少，公式要求 B 增加来维持 k 不变，于是你拿的 A 越多，需要付的 B 就越多，等于价格越买越贵。A pool holds 100 A and 100 B, so k is 10,000. You want to take out some A; A in the pool drops, and the formula requires B to rise to keep k constant. So the more A you take, the more B you must pay — meaning the price gets more expensive the more you buy.

配套工具（点开在主站打开）：Related tools (open on the main site):

📝 本节测验📝 Quiz

❓ 常见问题❓ FAQ

AMM 和普通挂单撮合哪个更好？Which is better — an AMM or an ordinary order book?

没有绝对好坏。AMM 胜在随时有报价、无需对手，适合链上;挂单撮合在大额和精细定价上更灵活。两者各有适用场景。There's no absolute better or worse. An AMM wins by always having a quote and needing no counterparty, which suits on-chain use; an order book is more flexible for large sizes and fine pricing. Each has its own use cases.

为什么小池子的币价容易被拉高拉低？Why is the price in a small pool easy to pump or dump?

因为池子浅，少量买卖就能大幅改变两种币的比例，公式随之把价格拉动很大。深池子则稳得多。Because the pool is shallow, even a small trade can greatly change the ratio of the two tokens, and the formula then moves the price a lot. A deep pool is far more stable.

AMM 里看到的价格是真实市场价吗？Is the price you see in an AMM the real market price?

它是这个池子按公式算出的价，可能和其他平台略有差异。跨平台价差过大时要留意，别只看单一池子的报价。It's the price this pool calculates by its formula, which may differ slightly from other platforms. Be cautious when the price gap across platforms is too large — don't rely on a single pool's quote.