The invention provides a method for judging the age of Yunnan ancient tea trees based on ground diameter, which comprises the following steps: (1) selecting Yunnan ancient tea trees which fall or dieby wind as representative samples, and measuring the ground diameter (cm); (2) sawing the ancient tea tree into a disc, and polishing the surface of the disc with a sand mill until the annual ring isclearly visible; (3) determining the number of annual rings in two vertical directions by using a winDENDROPRO annual ring analysis system, and finally taking the average value as the tree age of thetree; (4) using Origin 9.1 software to establish a scatter diagram for the original data, wherein the ground diameter is the abscissa x, and the tree age is the ordinate y; (5) performing curve fitting on the scatter diagram to obtain a function relationship between the ground diameter and the tree age of the Yunnan ancient tea tree; and (6) reckoning the tree age of the ancient tea tree to be measured according to the established function through actually measured ground diameter data. The invention provides a simple and convenient tree age judgment method by taking the ground diameter whichis easy to measure as a variable.