1、去掉角标

:deep(.el-textarea__inner) {resize: none !important; // 去除右下角图标
}

2、去除边框，并自定义背景色

  <el-inputref="textareaRef"v-model="tempContent":style="{'--el-border-color': 'rgba(255,255,255,0.0)','--el-input-focus-border-color': 'rgba(255,255,255,0.0)','--el-input-focus-border-width': '0px','--el-input-hover-border-color': 'rgba(255,255,255,0.0)','--el-input-hover-border-width': '0px','--el-input-bg-color': 'rgba(0,0,0,0.8)'}"type="textarea"placeholder="请输入":autosize="{ minRows: 8, maxRows: 20 }"class="custom-textarea"/>

效果图