Molybdenum phosphate(P/Mo=1.0) has been synthesized with ammonium molybdate and phosphoric acid under aqueous solution. The kinetics of ammoxidation of 3-picoline over the molybdenum phosphate catalyst were investigated with the variation of reaction temperature and partial pressure of 3-picoline, oxygen, and ammonia, respectively at atmospheric pressure. The catalytic activity was increased until 300 hrs on stream and then maintained until 500 hrs on stream under our experimental conditions. At the steady-state conditions, the rate equation of 3-picoline ammoxidation was shown as -r=kP^3-PP_NH3⁰P_O2^γ[γ=0.2;0.25≤PO₂(kPa)≤5 : =0;5≤PO₂(kPa)]. The correlation between the conversion of 3-picoline and the selectivity of 3-cyanopyridine had the proportional relationship. As the selectivity of 3-cyanopyridine increases, the selectivity of amide and acid decreases.