A thin film transistor, a manufacturing method thereof, an array substrate and an electronic device arc provided. The thin film transistor includes an active layer including multiple oxide layers which includes a channel layer, a transition layer and a first barrier layer, the channel layer is an layer with a highest carrier mobility, the channel layer is a crystalline or amorphous oxide layer, the transition layer is in direct contact with the channel layer, the first barrier layer is an outermost oxide layer, the first barrier layer and the transition layer are both crystalline oxide layers; a crystallization degree of the first barrier layer and a crystallization degree of the transition layer are greater than a crystallization degree of the channel layer, and a band gap of the first barrier layer and a band gap of the transition layer are larger than a band gap of the channel layer.