A process for preparing anthranilic diamide of Formula I, wherein, R 1 is CH 3, Br or Cl; R 2 is F, Cl, Br, or I; R 3a and R 3b are independently H, C 1 -C 4 alkyl or C 3 -C 6 cycloalkyl-C 1 -C 4 alkyl; R 3c is H or C 1 -C 4 alkyl; R 4 is Cl, Br, CF 3, OCF 2 H, OCH 2 CF 3, R 5 is F, Cl or Br; R 6 is H, F or Cl; Z is CR 7 or N; and R 7 is H, F, Cl or Br, said process comprising the steps of: a) obtaining a dione of Formula II by reacting a compound of Formula III, chloral hydrate of Formula IV and hydroxyl amine in the presence of at least one suitable reagent; or obtaining the dione of Formula II by cyclizing a compound of Formula IIIa in the presence of at least one suitable reagent; wherein the compound of Formula IIIa is obtained as an intermediate in the process step of reacting the compound of Formula III, chloral hydrate of Formula IV and hydroxyl amine in the presence of at least one suitable reagent; wherein, R 1 and R 3c are as defined herein before, b) oxidizing and halogenating the dione of Formula II simultaneously into an isatoic anhydride of Formula V using at least one oxidizing reagent and at least one halogenating reagent in the presence of at least one suitable acid; wherein, R 1, R 2 and R 3c are as defined herein before, c) reacting the compound of Formula V with an amine of Formula VI to obtain a compound of Formula VII in the presence of at least one suitable reagent; wherein, R 1, R 2, R 3a, R 3b and R 3c are as defined herein before, and d) reacting the compound of Formula VII and a compound of Formula VIII to the compound of Formula I in the presence of at least one suitable reagent; wherein, R 8 is OH, Cl, X or O-C 1 -C 4 alkyl; R 1, R 2, R 3a, R 3b, R 3c, R 4, R 5, R 6 and Z are as defined herein before, and wherein, the compound of Formula V may or may not be isolated. R 1 is CH 3, Br or Cl; R 2 is F, Cl, Br, or I; R 3a and R 3b are independently H, C 1 -C 4 alkyl or C 3 -C 6 cycloalkyl-C 1 -C 4 alkyl; R 3c is H or C 1 -C 4 alkyl; R 4 is Cl, Br, CF 3, OCF 2 H, OCH 2 CF 3, R 5 is F, Cl or Br; R 6 is H, F or Cl; Z is CR 7 or N; and R 7 is H, F, Cl or Br, a) obtaining a dione of Formula II by reacting a compound of Formula III, chloral hydrate of Formula IV and hydroxyl amine in the presence of at least one suitable reagent; or obtaining the dione of Formula II by cyclizing a compound of Formula IIIa in the presence of at least one suitable reagent; wherein the compound of Formula IIIa is obtained as an intermediate in the process step of reacting the compound of Formula III, chloral hydrate of Formula IV and hydroxyl amine in the presence of at least one suitable reagent; wherein, R 1 and R 3c are as defined herein before, obtaining the dione of Formula II by cyclizing a compound of Formula IIIa in the presence of at least one suitable reagent; wherein the compound of Formula IIIa is obtained as an intermediate in the process step of reacting the compound of Formula III, chloral hydrate of Formula IV and hydroxyl amine in the presence of at least one suitable reagent; wherein, R 1 and R 3c are as defined herein before, b) oxidizing and halogenating the dione of Formula II simultaneously into an isatoic anhydride of Formula V using at least one oxidizing reagent and at least one halogenating reagent in the presence of at least one suitable acid; wherein, R 1, R 2 and R 3c are as defined herein before, c) reacting the compound of Formula V with an amine of Formula VI to obtain a compound of Formula VII in the presence of at least one suitable reagent; wherein, R 1, R 2, R 3a, R 3b and R 3c are as defined herein before, and d) reacting the compound of Formula VII and a compound of Formula VIII to the compound of Formula I in the presence of at least one suitable reagent; wherein, R 8 is OH, Cl, X or O-C 1 -C 4 alkyl; R 1, R 2, R 3a, R 3b, R 3c, R 4, R 5, R 6 and Z are as defined herein before, and wherein, the compound of Formula V may or may not be isolated.