The soybean production chain is one of the main agribusiness products. In this context, the grain market is constantly expanding. Thus, it is important to carry out the characterization of soybeans and define their qualities. The objective of this study was to evaluate the quality of commercial soybean grains in post-harvest, as well as the economic losses in a crop in the municipality of Mojuí dos Campos, Pará. Two types of cultivars at 4280(IPRO) and 8644 (IPRO) were used, harvested on different days and plots.Data collection was carried out by monitoring the post-harvest process. The information regarding the grains was obtained through the classification report provided by the company accredited to classify the grains. The methods used were carried out in accordance with the Technical Regulation of Soybeans of Normative Instruction No. 11, of May 15, 2007, of the Ministry of Agriculture, Pecuária e Abastecimento (MAPA). Data were analyzed by PROC TTEST in SAS version 19.0 at a significance level of 5%. The results showed that, in the period of harvesting of cultivar 8644(IPRO), there was a higher rate of rainfall compared to the days of harvesting of cultivar 4280(IPRO). The total of discounted grains was 15.101t for the cultivar 4280(IPRO). The wet grain is the only parameter responsible for the discount in both cultivars. The total of discounted grains referring to cultivar 8644(IPRO) was 30.218t. The wet grains for the cultivar had the highest classification rate on the fourth day of harvest, with a total of 23.20%, being related to the decrease in the percentage of broken grains (1.60%) and a higher index of burnt/damaged grains. It is concluded that the cultivar 4280(IPRO) presented a lower grain discount compared to the cultivar 8644(IPRO). Consequently, cultivar 8644 presented greater economic damage to the property.