In response to the demand for in-situ online detection of non-soluble deposit density (NSDD) on high-voltage insulators in power systems, this study investigated a quantitative measurement method for the NSDD of insulator pollution simulation samples based on laser-induced breakdown spectroscopy (LIBS). Initially, a sample preparation method that simulates the natural accumulation of contaminants was developed, through which multiple insulator pollution simulation samples with small and uniformly distributed NSDD gradients were fabricated for the first time. Then, microscopic imaging and binarization processing revealed a "saturation" trend in the dust accumulation process on the sample surfaces, indicating that contamination completely covers the sample surface at an NSDD of approximately 3 mg/cm2. A correlation between the area ratio of dust coverage and amount of contamination was established. Furthermore, the spectral characteristics of different NSDD samples and the variation patterns of their characteristic spectral lines were studied, revealing that the spectral intensity of high NSDD samples decays at a faster rate with increasing detection delay compared with low-NSDD samples. Finally, calibration experiments were conducted on the simulated samples using a direct focusing LIBS system. Based on the characteristics of dust accumulation on the samples, a piecewise calibration method is proposed, utilizing quadratic and linear fitting to establish calibration models for two distinct dust accumulation stages. The detection limit of this method is 0.0043 mg/cm2, with a quantification limit of 0.0129 mg/cm2. The coefficient of determination for the calibration models reached 0.99 and 0.97 in the two stages, respectively, with a root mean square error of 0.1578 mg/cm2. The methodologies presented in this paper closely approximate the actual detection conditions of real insulators in terms of sample preparation and experimental systems, thereby providing technical support for the field-based in-situ detection of NSDD on high-voltage insulators in power systems.