The embodiment of the invention discloses a preparation method for a semiconductor power device structure, and a structure. A Trench layer of a conventional lateral power device Trench LDMOS structure is provided with a plurality of longitudinal metal field plates at different depths, and a drift region is provided with a heavily-doped n-type layer. In order to improve the breakdown voltage of a device, the metal field plates with different lengths at different layers can introduce a plurality of new electric field peak values in a drift region, and enables a surface high electric field to be introduced into a body, thereby protecting the surface of the device from being broken down in advance. After complete loss, the heavily-doped n-type layer improves the surface charge density of the Trench layer, improves the electric fields of the Trench layer and the drift region, and improves the breakdown voltage of the device. In order to reduce the conduction resistance of the device, a deep oxygen Trench layer reduces the length of the lateral drift region.