But Steve Clarke’s high-flying side did not have it all their own way against the League One outfit and were relieved when subsitute Chris Burke notched their second with 12 minutes remaining to secure their passage into the fifth round draw.
Kilmarnock defender Stuart Findlay opened the scoring after 19 minutes with a stunning volley from just inside the box but Forfar had their moments as they chased an equaliser with Jamie Bain going close for them.
But Killie held firm and got the job done as they marched on in the Scottish Cup.
Kilmarnock manager Steve Clarke had told they fans they would be booing him if they jeered Jordan Jones after the winger signed a pre-contract with Rangers.
Jones had angered many of the Killie support when he tweeted joining Rangers was a “dream come true” and used the hashtag “WATP”, Gers slogan “We are the people” but the fans took the manager’s words on board as there were no boos when his name was announced in the line-up or when he was in possession.
Forfar were hoping to cause a Scottish Cup shock and they were first to threaten when Thomas Reilly fired a volley from inside the box just over the crossbar.
Kilmarnock made the breakthrough after 19 minutes through a stunning Findlay strike.
Forfar’s Ross Meechan conceded a corner when he should have just let the ball go out of play. Killie worked the corner with Jones picking up possession, cutting infield and while his shot was blocked the ball broke for Greg Kiltie.
Kiltie played it into the path of Findlay and from just inside the penalty area the big defender unleashed a volley that flew last Marc McCallum.
McCallum then pulled off a fine save to deny Rory McKenzie doubling Killie’s lead.
Four minutes before the break Forfar came close to a leveller when Murray Mackintosh drove forward and let fly with a strike from 25-yards that Jamie MacDonald did well to turn round the post.
Just after the interval Jamie Bain went close with a crisp volley that flew just wide.
McCallum kept Forfar in the tie when he pulled off a fine save to deny Killie. Iain Wilson won the ball inside his own half and drove forward and then slid a clever ball to Kiltie but McCallum rushed off his line to block his shot.
Bain drilled a ball across the face of goal but there were no takers for Forfar and the midfielder then went close with a shot.
Killie made sure there would be no shock when subs Mikael Ndjoli and Burke combined for their second. Ndjoli played a ball across the face of goal and Burke slide in to turn it home.