This study was conducted to compare with the multi-residue analysis method for reduced a matrix effect in three agricultural products, such as orange, green pepper and brown rice. QuEChERS method involves single-phase extraction of 10 g sample with 10 mL acetonitrile. On the other hand, the improved method extracted 10 g of sample with 50 mL acetonitrile. Clean-up step used in the QuEChERS method was the d-SPE using PSA, but C18 of SPE cartridge was used for the improved method. As a result, both methods were similar in linearity and limit of quantification. The ratios that satisfy the Codex guideline were 85% of total pesticides for AOAC QuEChERS method and 88% for the improved method. Matrix effects showed different results, however, the improved method was found to produce least matrix effect. Average matrix effect QuEChERS method was -38%, and those of the improved method was -10%. Comparison of matrix effects for different agricultural products showed high variability for some residues such as dimethylthiocarbamate. It was indicated that the amount of co-extracting compounds that cause ionization suppression of pesticides depends on the agricultural products as well as on the sample preparation method employed. As a conclusion, the improved method appears to be a more suitable method because it can reduce the matrix effect rather than the QuEChERS method.