Through this link, I found the cause of similar problems:
> gswin32c -h としてみると,
TeX Live に入っている Ghostscript は,直接「gswin32c」というコマンドで呼び出すことを想定していません。
あくまでそれは TeX と一緒に使うためのものなので,「rungs」という名前で呼び出すことになっていて,
外部ツールから呼び出すことはサポート外と書かれています。
tlpkg フォルダの中の tlgs/README.TEXLIVE を読んでください。Web 上で読むならここですね。
Translate this into English through Google translate as follows:
Ghostscript included in TeX Live is not supposed to be called directly with the command "gswin32c".
It is only for use with TeX, so it is called as "rungs", and calling
from an external tool is not supported.
Read TLGS / readme.texlive in the tlpkg folder. It's here if you read on the web.
I found out how to correctly configure Matex in the environment of texlive2019 as follows:
<< MaTeX`
ClearMaTeXCache[];
(*MaTeX/tutorial/ConfiguringMaTeX*)
MaTeX`Developer`ResetConfiguration[]
ConfigureMaTeX[
"pdfLaTeX" -> "D:\\texlive\\2019\\bin\\win32\\xelatex.exe",
"Ghostscript" -> "D:\\texlive\\2019\\bin\\win32\\rungs.exe"]
MaTeX["\\ce{2H2 + O3 ->T[\\text{燃烧}] 2H2O}",
"Preamble" -> {"\\usepackage[version=4]{mhchem}",
"\\usepackage{ctex}"}, FontSize -> 20]

We can also download the independent Ghostscript from here and configure Matex after installation:
ConfigureMaTeX[
"pdfLaTeX" -> "D:\\texlive\\2019\\bin\\win32\\xelatex.exe",
"Ghostscript" -> "C:\\gs\\gs9.50\\bin\\gswin32c.exe"]
In this way, the correct output can also be obtained.