---
title: "How to Tell if a Cannon Is Good or Bad in Xiangqi · Xiangqi Master"
description: "Count its available screens and its actual targets, not just its raw mobility. A cannon with no useful screen anywhere on its lines is doing almost nothing, whatever it looks like."
url: https://xiangqimaster.com/blog/how-do-you-know-if-a-cannon-is-good-or-bad
updated: 2026-09-22
source: Xiangqi Master (https://xiangqimaster.com)
license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
---

# How do you know if a cannon is good or bad in a given position?

These answers restate the rules implemented by our open-source engine, which follows the WXF laws and is regression-tested against the official 110-diagram repetition casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it against the engine before publishing.

> Direct answer
>
> Count **screens and real targets**, not squares. A cannon that can reach far along an empty line is not doing anything if nothing sits one piece away from a genuine target; a cannon boxed in close to home but sitting exactly one screen from the enemy general is doing a great deal. Raw mobility is close to meaningless for this piece.

## The quick test

Ask two questions of every cannon on the board: which of its lines currently has exactly one piece on it, and what sits beyond that piece. A cannon that answers "none" to the first question is contributing nothing right now, however open its other lines look.

## Watching it change move to move

Because any piece landing on a line can switch a cannon's threat on or off, in the same way [moving requires a clear line while capturing needs exactly one piece on it](https://xiangqimaster.com/blog/can-a-cannon-move-without-a-screen), a cannon's quality is not fixed the way a chariot's is. Reassess it after every move nearby, not just once at the start of your calculation.

## Related questions

Is a cannon with no screens simply worthless?

Temporarily weak, not worthless; the position can change with the very next move on either side.

Should I judge a cannon by how many squares it controls?

No, that measures its potential to move, not its ability to threaten anything, which is a different question entirely.

## Related xiangqi resources

How the cannon moves

Captures only by jumping exactly one screen

Cannon tactics

Screens, batteries and discoveries

What the pieces are worth

And the three times the numbers stop being true

## Try it on a real board

Reading an answer is one thing; playing it is another. Free, instant, and nothing to install.