In this work we propose a new indicator to classify the best period for longan fruit harvest, based on measurements of its longitudinal and transversal axis during growth. Shape analysis based on area per volume ratio (A/V) and sphericity show that those indicators stabilize after during longan growth period, independently of variety, in a specific environment. As sphericity increases 6% during fruits growth, A/V ratio decreases dramatically (75%) closing to maturity, at 120 days after anthesis. The first derivative of A/V ratio indicates three distinct phases that are related to the growth phases of fruits. We believe that those shape indicators could be used to probe the right point of longan fruits maturity in different environments in a quantitative way.