The 32-year-old only spent five months in China having left Genoa in July, but he was still able to score five goals to help Evergrande win the league title.
However, the lure of Serie A proved too much for the Italy international and he returns to the Artemio Franchi three years after leaving.
During his first spell with the club Gilardino scored 59 goals in all competitions and improving on that is his main priority.
"Today's a big day for me, coming back to Florence," he told the club's official website. "I'm really happy to be here. It's great to be back and I'm raring to go.
"I want to prove myself in Serie A again after five months away. I'm really up for it and I feel good physically.
"I think the objective is to get back up among the very best so that we can be involved in the Champions League."
Gilardino completed the details of his loan move on Monday after watching Fiorentina draw 1-1 with Roma on Sunday.
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