In view of the important influence of solid forms on the production and use of agrochemicals, it is crucial to develop accurate and useful qualitative and quantitative analysis systems for the solid forms of agrochemicals. However, this type of work is rare, and a corresponding research template is urgently needed. This work constructs and applies a qualitative and quantitative analysis system for three boscalid polymorphs (form I, form II and form H1) using two solid-state analytical methods (X-ray powder diffraction and attenuated total reflectance-Fourier transform infrared spectroscopy) coupled with chemometric tools. First, the preparation, characterization and analysis of the three polymorphs were carried out. Then, a qualitative analysis system for classifying the three polymorphs and their mixtures simultaneously was established via principal component analysis using suitable preprocessed spectrum regions. It was demonstrated that the first principal component and second principal component of the X-ray powder diffraction patterns and attenuated total reflectance-Fourier transform infrared spectra were sufficient to classify samples containing different solid forms into distinct categories. Among the quantitative analysis systems for designed mixtures of ternary solid forms established using principal component regression and partial least squares regression with different preprocessed spectrum regions, the partial least squares regression analysis system based on the standard normalized variate-preprocessed 1700–400 cm⁻¹ region of the attenuated total reflectance-Fourier transform infrared spectra has the best quantitative ability for the three polymorphs, with low values of root mean square error of calibration (1.402–2.045%), root mean square error of prediction (2.106–2.469%), overall method error (2.775–3.195%), limit of detection (2.616–3.707%) and limit of quantification (7.926–11.234%), and high values of correlation coefficient (not less than 0.993). The abovementioned qualitative and quantitative analysis system of boscalid polymorphs is accurate and useful, which could provide good guidance for the development of agrochemical solid form analysis and control.