Otdfbt

I came across this sentence in my japanese practicing material (the point is I didn't make up the sentence so I assume it's correct or at least commonly used)

日本についてのアンケートを中国人100人に行った。

and It doesn't make sense to me. What I guess the sentence means (out of the meaning of the used vocabulary) is something like: "according to a Japanese survey, the population of China has grown to 100 people". However I would phrase it as something along those lines:

日本のアンケートによると、中国人は100人に行った。

I do not understand the gramatical structure of the sentence, nor I'm sure if I guessed the meaning correctly. How does を relate to the only verb appearing in the sentence (行く)?

This is the sentence as it appears in my exercise sheet (number 6) as a multiple choice exercise. Note that there are other possible choices rather than アンケート, but they make no sense to me at all:

Thank you.

The verb is 行おこなう not 行く。
They both conjugate to 行った in the past tense so it can look confusing, but as you have just experienced, the context can make it clear which one it is.

日本についてのアンケートを中国人100人に行おこなった。
Carried out/Conducted a survey about Japan on 100 Chinese people.

The sentence:

「日本についてのアンケートを中国人100人に行った。」

makes perfect sense.

The reason that it does not to you is that you are "misreading" 「行った」 as 「いった」.

This verb is 「行おこなう」 meaning "to perform", "to conduct", etc.

「アンケートを行おこなった」 is a perfectly natural phrase meaning "conducted a survey/questionnair".

「中国人100人に」, of course, means the same thing as 「中国人100人に対して」.

Putting everything together, we have:

"We/They conducted a survey with 100 Chinese people on the subject of Japan."

Finally, your sentence 「日本のアンケートによると、中国人は100人に行った。」 makes no sense regardless of how you are reading the 「行った」, I am afraid.