Nuclear magnetic resonance (NMR) technique has been broadly used in probing plant water relations. However, the relationship between NMR parameters and photosynthetic traits is still not clear. An NMR system was constructed to perform non-imaging relaxation measurement or magnetic resonance imaging on wheat non-invasively and non-destructively. It was found that from the onset of leaf senescence to the degradation stage, the average T2 relaxation time (T2,mean) increased gradually and the chlorophyll content decreased, while the amplitude (A) of T2 relaxation spectrum and water content kept stable. When wheat leaves approached cell death, all of the above mentioned NMR and physiological parameters decreased to its minimum value. It was deduced that A and the water content of wheat leaves were linearly correlated. On the other hand, T2,mean was related with leaf senescence status. Therefore, non-imaging T2 relaxation technique was thought a fast and powerful method to estimate the senescence status of wheat leaf. In addition, T1 weighted imaging and T2 weighted imaging could represent leaf physiological status directly based on the relaxation property. T1 weighted imaging was comparatively time-saving, whereas T2 weighted imaging was much more sensitive to leaf aging.