Abstract: Using the way of joining the investigation in the orchard,chemical analysis and experiment of applying amount of the nitrogen fertilizer in the fields to study on the technique of the nutrition diagnosis of nitrogen in Ginkgo biloba L. The result shows the best diagnostic form in soil is available N of soil. The diagnostic index (mg/kg) is: high115.2, middle 78.8～115.2 and low 78.8. The best diagnostic period of the nutrition diagnosis of nitrogen in Ginkgo biloba L plant is in July and the best position is in the 8 th leaf of reverse order in the long branch. The diagnostic form is total nitrogen. Its diagnostic index (N%)is: high2.04, middle 1 80～2.04 and low1.80.