•A novel adsorbent was prepared for magnetic solid phase extraction.•The adsorbent was hydrophilic–lipophilic balanced magnetic polymer, which can extract analytes with different polarities.•Varieties of experiment factors were optimized and selected.•Good enrichment factors (724–925) were obtained.•This method has been successfully applied in the analysis of real water samples.In this study, a novel hydrophilic–lipophilic balanced magnetic nanoparticle, magnetic poly(divinylbenzene-co-N-vinylpyrrolidone) (HLB-MPNP) was successfully synthesized and applied for the extraction and determination of triazine and organochlorine pesticides in environmental water samples. The specific ratio of two monomers, hydrophilic N-vinylpyrrolidone and lipophilic divinylbenzene, endowed the magnetic nanoparticles with hydrophilic–lipophilic balanced character, which made it capable of extracting both polar and nonpolar analytes. The experimental parameters affecting extraction efficiency, including desorption conditions, sample pH, sample volume and extraction time were investigated and optimized. Under the optimum conditions, good linearity was obtained in the range of 0.20–10 μg L−1 for triazine herbicides and 5.0–100 ng L−1 for organochlorine pesticides, with correlation coefficients ranging from 0.994 to 0.999. The limits of determination were between 0.048 and 0.081 μg L−1 for triazine herbicides and 0.39 and 3.26 ng L−1 for organochlorine pesticides. The proposed method was successfully applied in the analysis of triazine and organochlorine pesticides in environmental water samples (ground, river and reservoir).