.welcome_month_li {
width: 200px;
height: 100px;
display: table;
}
.welcome_month_noData {
width: 100%;
height: 100%;
text-align: center;
display: table-cell;
background: red;
}
<div class="welcome_month_li ">
<div class="welcome_month_noData">
文字居中
</div>
</div>