The invention discloses an automatic growing tray feeding apparatus of a seedling throwing machine. The automatic growing tray feeding apparatus comprises a fixed bracket, a growing tray conveying mechanism, a slide platform, a guide rod, a lifting mechanism and a plurality of growing trays, wherein the growing tray conveying mechanism is obliquely installed at the fixed bracket, the slide platform sleeves the guide rod, the slide platform is connected with the lifting mechanism, and the plurality of growing trays are installed at the slide platform in a row from bottom to top; and when the growing trays are fed to the growing tray conveying mechanism, the plurality of growing trays disposed above the growing tray conveying mechanism descend and successively pass through the growing tray conveying mechanism. The automatic growing tray feeding equipment is researched and developed for the seedling throwing machine represented by a pneumatic orderly throwing transplanter, so that the throwing transplanter can be operated by a single person to perform the field throwing transplanting work, the step of the traditional method for manually feeding bowl-grown seedling growing soft trays can be substituted, the number of people for supporting the field work of the throwing transplanter can be reduced, the labor intensity is alleviated, and the working efficiency of the throwing transplanter can be improved.