To produce the high quality tomato fruits, plants are grown in soilless culture with the special features by controlling the nutrient solution. This effort highly requires real-time bioinformation of fruit internal properties during growth for feedback in routine control of the nutrient solution. The dry matter (DM) and starch content of the growing fruits are mainly correlated to ripe-stage soluble solids content (SSC) as an important quality parameter. In this study, the “on-site” near infrared (NIR) measuring system was successfully developed as a nondestructive method for determination of DM and starch content in growing fruits. As the temperature of fruit in field could not be controlled, the problem could be solved using a calibration model with temperature compensation. Here, the high performance of this measuring system for monitoring on-plant fruit was also demonstrated. The equations developed from the monitoring results of DM and starch content could be used to predict the SSC of ripen fruits. The use of “on-site” NIR measuring system developed, makes it possible to control and modify the nutrient solution (e.g. EC level) based on the internal properties of immature fruits to produce tomatoes at the desired SSC level.