A LTPS TFT and a TFT substrate are disclosed. The LTPS TFT includes: a substrate; a first gate arranged on the substrate; a polysilicon layer arranged on the substrates, and the polysilicon layer covers the first gate, wherein the polysilicon layer comprises a source area, a drain area, and a trench area formed between the source area and the drain area; a second gate arranged on the polysilicon layer; wherein when the LTPS TFT has been driven, the first gate and the second gate are respectively applied with a first voltage and a second voltage, and a polarity of the first voltage is opposite to the polarity of the second voltage. In this way, the feed through voltage may be reduced such that the TFT performance is enhanced.