The present invention refers to a method for online monitoring, without the need for sampling and in real time, the precipitation of inorganic salts in aqueous streams related to the petroleum industry. This method is based on the use of the NIR technique with the aid of the FBRM technique. The NIR technique makes it possible to collect spectra and monitor the variation in absorbances, concerning the formation of particles of inorganic salts in the aqueous solution, while the FBRM technique provides the number and size of precipitated particles through the reflection of light emitted by a beam of Incident light in aqueous systems in the presence of different solvents, pH conditions, supersaturation, temperature and pressure. Thus, a set of collected NIR spectra is correlated with data provided by FBRM through a mathematical (chemometric) treatment and mathematical models based on artificial neural networks combined with principal component analysis were employed to estimate the quantity and size distribution of particles precipitated over time. The application of these process analyzers helps to understand the formation and growth of inorganic salt particles from the produced water (rich in carbonates and sulfates), which can precipitate at different stages in oil production and transportation facilities.