Twenty nine novel N-4-methyl-1,2,3-thiadiazole-5-carbonyl-N′-phenyl ureas were designed and synthesized, and their structures were confirmed by proton nuclear magnetic resonance (1H NMR), infra red spectroscopy (IR) and high-resolution mass spectroscopy (HRMS). Compounds V-9, V-11, V-12, V-15, V-19, V-21, V-22 and V-24 exhibit excellent activity against Culex pipiens pallens. Compounds V-12 and V-22 present good insecticidal activity against Plutella xylostella L. Their median lethal concentrations (LC50) are 164.15 and 89.69 mg·L−1, respectively. Compound V-11 also has potential wide spectrum of fungicide activity. Its median effective concentrations (EC50) detected from 3.82 µg·mL−1 against Physalospora piricola to 31.60 µg·mL−1 against Cercospora arachidicola. Compounds V-15 and V-24 show outstanding induction activities as same as positive controls TDL and ningnanmycin, furthermore V-24 has the highest induction activity of 41.85%±4.43%. To elucidate the structure activity relationship in these compounds, a 3D-QSAR model has been built. The established model showed a reliable predicting ability with q2 values of 0.643 and r2 values of 0.982.