The square pond is as clear as a mirror. "Mirror" and "sword" are the same meaning. "Half acre square pond" is as clear as a mirror, and "sky and clouds" are reflected by it. Therefore, the poet thinks that reading is the same. The water in the "half acre square pond" is deep and clear, so it can reflect the "sky light and clouds"; On the other hand, if it is shallow and dirty, it cannot be reflected, or it cannot be accurately reflected. But the poet didn't stop there. He further asked why it was so "clear" that "sky and clouds" could be reflected. There is no way to answer this question by looking at this square pond in isolation. The poet then opened his eyes and looked from a distance. Finally, he saw the "source" of "Fangtang" and found the answer. It is precisely because "Fangtang" is not passive water, it has inexhaustible "source" and continuously delivers "living water" to it. This "square pond" will never be exhausted, stale, dirty, deep and clean because of the continuous input of "flowing water from the source". "Qing" can not only embody "sky and clouds", but also embody such detailed modality as "sky and clouds" and "* * *". This is the image and ideological significance of this little poem.