Arsenal threatened to spoil the party by taking a shock lead after 26-minutes when Ashley Cole sprinted down the left, had a shot parried but knocked home the rebound.
But just 35-seconds after the break Kachloul got his first league goal since the opening day of the season chipping in from the left edge of the area.
The Gunners hit back on 54-minutes when Thierry Henry broke clear and squared for Freddie Ljungberg to slot home unmarked.
But Saints levelled again on the hour when Kachloul prodded into an empty net following a firm challenge on the keeper by James Beattie.