The invention provides an automatic transplanter chassis for plug seedlings. The chassis comprises a chassis support, height adjusting devices and a row spacing adjusting device; the chassis support is installed on wheels through the height adjusting devices, and the height adjusting devices are used for adjusting the height of the chassis support; the row spacing adjusting device is installed onthe chassis support, provided with a planting mechanism, and used for adjusting the transplanting row spacing. Wheel span adjusting devices comprise the front wheel span adjusting device and the rearwheel span adjusting device, and the height adjusting devices comprise the front wheel height adjusting device and the rear wheel height adjusting device. By means of the automatic transplanter chassis, lifting and falling of the chassis support can be achieved to meet the requirements of different crops for planting depths, and different planting row spacings are adjusted to meet the requirementsof different crops for planting rowing spacings; different wheel spans can be adjusted to adapt to different ridge widths.