With Sharepoint Designer, edit the page of list view. Add xsl template as below to override original template. Source template could be found at
http://[servername]/_layouts/xsl/fldtypes.xsl.
<xsl:template name="FieldRef_Note_body" ddwrt:dvt_mode="body" match="FieldRef" mode="Note_body">
<xsl:param name="thisNode" select="."/>
<div dir="{@Direction}" class="ms-rtestate-field">
<xsl:value-of select="concat(substring($thisNode/@*[name()=current()/@Name],0,50), ' ...')" disable-output-escaping="yes"/>
</div>
</xsl:template>