The invention discloses a process for printing and dyeing leather by the aid of watermelon juice. The process includes steps of preparing watermelon red pigments by the aid of extraction and purification methods and the like; preparing watermelon red dye from watermelon red, dyeing the leather which is subjected to rare-earth mordant dyeing, and coating ox horn oil on the leather. The process has the advantages that the natural dye and leather surfaces are treated, the leather is dyed by the aid of the natural dye, and accordingly dyeing effects can be improved.