使用li将li：：内容置于中心位置

<ul class="centered-list">
  <li><span>内容1</span></li>
  <li><span>内容2</span></li>
  <li><span>内容3</span></li>
</ul>

.centered-list {
  display: flex;
  justify-content: center;
  align-items: center;
  list-style-type: none;
  padding: 0;
}

.centered-list li {
  text-align: center;
}

.centered-list li span {
  display: inline-block;
}

<ul class="centered-list">
  <li><span>内容1</span></li>
  <li><span>内容2</span></li>
  <li><span>内容3</span></li>
</ul>

.centered-list {
  position: relative;
  list-style-type: none;
  padding: 0;
}

.centered-list li {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  text-align: center;
}

.centered-list li span {
  display: inline-block;
}