To insight the atmospheric fate of 2-methyl-3-pentanone (2M3P), 3-methyl-2-pentanone (3M2P) and 4-methyl-2-pentanone (4M2P), three widely used compounds in the industry, the kinetic and products of reactions of OH radical with above mentioned ketones were investigated using two complementary techniques: Pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) and continuous photolysis simulation chamber. Kinetic studies were investigated using absolute rate method and relative method (rate constants below are in 10-12 cm 3 molecule-1 s-1): Absolute rate method (PLP-LIF) at 253-376 K was used to measure: k(OH+2M3P)= 3.57±0.05. In a 200 L simulation chamber, relative rate method with four reference compounds (propane, n-butane, n-hexane and cyclohexane) at 293±1 K was used to measure: k(OH+2M3P)= 3.41±0.15, k(OH+4M2P)= 10.56±0.32 and k(OH+3M2P)= 5.88±0.28. With a typical tropospheric OH concentration of 1×10 6 molecule cm-3 , the following tropospheric lifetimes toward OH reaction (τ=1/k[OH]) awee estimated: 3.3 days, 1.9 days and 1.1 days for reaction of OH radical with 2M3P, 3M2P and 4M2P, respectively. Products studies were conducted in a 7300 L simulation chamber using FTIR, PTR-Tof-MS, UHPLC and GCMS. Then, acetone plus acetaldehyde, 2-butanone plus acetaldehyde plus 2,3butanedione and acetone plus 2-methylpropanal were identified as products for the reactions of OH radical with 2M3P, 3M2P and 4M2P, respectively, in the presence of NOx. The acetone and acetaldehyde formation yields were determined to be 79.8±3.0 % and 104.3±10.0 %, respectively, from OH+2M3P; 2-butanone and acetaldehyde and 2,3-butanedione formation yields were determined to be 39.8±1.9 % and 109.2±6.1 % and 2.5±1.8 %, respectively, from OH+3M2P; acetone and 2-methylpropanal formation yields were determined to be 87.4±7.0 % and 10.7±4.8 %, respectively, from 4M2P+OH. In addition, CO and HO2 radical were also recommended to be the products from the OH reaction with these three studied ketones, which are believed to be the important species in the lower troposphere. The possible reaction mechanisms are discussed and compared with these product formation values, and it provides direct evidence that the H-atom abstraction rate and branch ratio depend on the CHx position to the >C=O group, which corresponds to the product formation yields.