Trehalose is a non-reducing disaccharide widespread in organisms, including bacteria, fungi, yeast，insects, invertebrates and plants. It is not only a carbohydrate reservoir but also a multifunctional molecule. Trehalose, which have some connections with hormones, too, has been recognized as a signaling molecule to initiate signal transduction cascades that result in a series of cellular responses such as altering gene expression and enzymatic activities. Increasing the accumulation of trehalose in plants by both gene engineering and exogenously supplied trehalose can improve stress tolerance of plants，this offers a novel strategy for improving stress tolerance in crop plants. This article reviews the current achievements in trehalose-mediated signal transduction.