The invention discloses a leaf water near infrared non-destructive testing device in a light open environment, comprising a modulation light source, a testing circuit and calculating and processing equipment, wherein the modulation light source is used for launching alternating current optical signals with modulated light intensity to a leaf according to an alternating current rule, the testing circuit is used for converting the alternating current optical signals permeating through the leaf to spectroscopic data, and the calculating and processing equipment is used for calculating the water concentration of the leaf from the spectroscopic data. The invention also discloses a leaf water near infrared non-destructive testing method in the light open environment, comprising the following steps of sequentially illuminating two lights with preset wavelengths, which are a first light and a second light, onto the surface of the leaf through optical fibers; converting the two lights which transmitting the leaf to first spectroscopic data and second spectroscopic data; calculating the water concentration of the leaf according to the two kinds of spectroscopic data. The device has simple structure, and can carry out testing in the light open environment and eliminate attenuation caused by light absorption and scattering of a leaf background in the process of water testing to enable a measured value of the water concentration to be more accurate.