In order to find new pyrazol-5-yl-carbonyl-heterocycles lead compounds, 12 pyrazolylheterocycles were synthesized from 3-ethyl-1-methyl-4-substitute-5- pyrazolecarboxylic acid chloride and nitrogen heterocyclic compounds such as 2-thiazolidone, 2-thiazolidinone, 2-oxazolidinone, etc. The structures of compounds obtained were confirmed by ¹H NMR, IR, MS spectra and elemental analysis. The crystal structure of 3-(3-ethyl-1-methyl-4-nitro-1H-pyrazol-5-yl-carbonyl)oxazolidin-2-one (3k) was deter-mined by X-ray diffraction analysis. 3k belongs to the monoclinic system with space group P2₁/n (#14) and cell dimensions: a＝1.52175(3) nm, b＝0.52970(1) nm, c＝1.58185(3) nm, β＝104.893(4), V＝1.2323(4) nm³, Z＝4, D_c＝1.45 g/cm³, F(000)＝560.00, R₁＝0.064, wR₂＝0.193. The results of biological tests indicated that, at 25 mg/L, 3-(3-ethyl-1-methyl-4-nitro-1H-pyrazole-5-carbonyl)thiazolidin-2-one (3c) and 3-(3-ethyl- 1-methyl-4-nitro-1H-pyrazole-5-carbonyl)-2-thiono-thiazolidine (3g) showed inhibitory activities of 40% against Pyricularia oryzae. At 500 mg/L, 3-(3-ethyl-1-methyl-4-bromo-1H-pyrazol-5-yl-carbonyl)thiazolidin-2-one (3d) and 3-(3-ethyl-1-methyl-4-bromo-1H-pyrazol-5-yl-carbonyl)oxazolidin-2-one (3l) showed in-hibitory activities of 53.37% against Nephotettix cincticeps.