In this study, we proposed a miniaturized system that can detect chlorophyll a/b ratio and their content simultaneously to measure the health condition of plants. In order to solve the problems of general measurement systems such as large-scale equipment and fracture measurement, a filter-free multiple wavelength sensor was used to evaluate the current ratio due to wavelength changes. Current characteristics demonstrated that the sensor due to the chlorophyll a/b ratio and changes in their concentrations are proportional to the spectral characteristics. As a result of measuring the extracted chlorophyll and tomato leaves, the value of the centroid wavelength of the transmission spectrum showed the current ratio and linear data of the sensor. The proposed method enabled simultaneous measurement of the total amount of chlorophyll and its a/b ratio of plants with a non-destructive and compact device and expected to be applied to the agricultural field.