Pineapples are not only nutritious, but also have significant economic importance in Taiwan. Traditional technique used to determine the fruit’s quality is by hitting the fruit with palm. However, such method requires experience and is highly dependent on the condition of the fruit. More importantly, decisions made are often subjective. This research used near infrared spectroscopy to develop a fast and non-destructive method to measure the quality of pineapples. Tai-Nung No. 17 pineapple was used in this research to construct the calibration equation. During the experiments, pineapple samples are separated into three sections: top, middle, and bottom. Optical measurements are taken around each section in 90 degree increments, with a total of 131 samples. A multivariate model was then established by mathematical pre-treatments and modified partial least squared regression. Results showed strong correlation between constituents and optical spectrum, with a coefficient of determination r_c²=0.78,r_p²=0.747,SEP=1.142°Brix,RPD=1.803. Future experiment aims to increase the predictability of spectrum model by enhancing experimental methods, increasing sample size as well as minimizing experimental error.