The deficiencies of essential macronutrients of nitrogen (N) and potassium (K) usually affect the production of chlorophyll, cause imbalances in plant growth and drastically most importantly affect the quality and yield of agricultural products. A new N/K deficiency diagnostics method was proposed based on chlorophyll distribution features of the whole cucumber leaf. N/K deficient cucumber plants and control plants were grown under nonsoil conditions with special nutrient supply. Chlorophyll distribution maps of N deficient leaves, K deficient leaves and control leaves were determined by using hyperspectral imaging technology and genetic algorithm, and distribution features extracted from the chlorophyll distribution maps were employed to diagnose N/K deficiencies. Chlorophyll distribution features (the mean value of all pixels in leaf center region and the number of pixels with low chlorophyll content in the leaf edge region) were extracted. A diagnostic method based on these features were obtained with total diagnostics rates of 95% for N/K deficiencies. The result indicated that the extracted chlorophyll distribution features could be employed to diagnose N and K deficiencies in cucumber plants.