模板 `.cls` 文件中与定理环境相关的是 ```tex % 定理环境 \newtheoremstyle{break}% name {}% Space above, empty = `usual value' {}% Space below {\itshape}% Body font {}% Indent amount (empty = no indent, \parindent = para indent) {\bfseries}% Thm head font {.}% Punctuation after thm head {\newline}% Space after thm head: \newline = linebreak {}% Thm head spec \theoremstyle{plain} \newtheorem{algo}{\sjtu@label@algo~}[chapter] \newtheorem{thm}{\sjtu@label@thm~}[chapter] \newtheorem{lem}[thm]{\sjtu@label@lem~} \newtheorem{prop}[thm]{\sjtu@label@prop~} \newtheorem{cor}[thm]{\sjtu@label@cor~} \theoremstyle{definition} \newtheorem{defn}{\sjtu@label@defn~}[chapter] \newtheorem{conj}{\sjtu@label@conj~}[chapter] \newtheorem{exmp}{\sjtu@label@exmp~}[chapter] \newtheorem{rem}{\sjtu@label@rem~} \newtheorem{case}{\sjtu@label@case~} \theoremstyle{break} \newtheorem{bthm}[thm]{\sjtu@label@thm~} \newtheorem{blem}[thm]{\sjtu@label@lem~} \newtheorem{bprop}[thm]{\sjtu@label@prop~} \newtheorem{bcor}[thm]{\sjtu@label@cor~} \renewcommand{\proofname}{\bfseries\sjtu@label@proof} ``` 因为最后一次调用的定理样式是 `\theoremstyle{break}`，所以你自己定义的定理环境也是 `break`。而根据 `break` 的定义，定理名之后会换行 ```tex {\newline}% Space after thm head: \newline = linebreak ``` 解决方案：在自己定义定理环境之前，使用 `\theoremstyle{...}` 切换定理样式。