A compound of Formula or a pharmaceutically acceptable salt or a stereoisomer thereof: wherein R 1 is selected from the group consisting of 6 to 7 membered saturated N-containing fused heterocyclyl, 7 to 10 membered N-containing spiro heterocyclyl and 7 to 8 membered N-containing bridged heterocyclyl; each attached to pyrimidyl via nitrogen and optionally substituted with a substituent selected from the group consisting of halogen, cyano, amino, hydroxyl, C 1-6 alkyl, halo C 1-6 alkyl, hydroxyl C 1-6 alkyl and C 1-6 alkoxyl, wherein the number of the substituent is 1 to 4; R 3 is -M-R 7, M is selected from a single bond and C 1-6 alkylene, R 7 is selected from the group consisting of phenyl, tetrahydrofuranyl, tetrahydrothienyl, tetrahydropyrrolyl, imidazolidinyl, pyrazolidinyl, piperidinyl, morpholinyl, piperazinyl, 2-oxo-azacycloheptanyl, 2-oxo-piperazinyl, furanyl, dihydrothienyl, dihydropyrrolyl, dihydrooxazolyl, dihydropyrazolyl, thienyl, pyrrolyl, imidazolyl, thiazolyl, pyrazolyl, pyrimidyl, pyridyl, pyrazinyl, oxazolyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, naphthyl, indolyl, benzimidazolyl, 2,3-dihydrobenzfuranyl, quinolinyl, benzo[ d][1,3]- meta -dioxa-cyclopentenyl, 7 to 10 membered spiro cyclyl, 7 to 10 membered bridged cyclyl, 7 to 10 membered spiro heterocyclyl and 7 to 10 membered bridged heterocyclyl; each optionally substituted with substituent L 2, said substituents L 2 is selected from the group consisting of halogen, hydroxyl, cyano, amino, C 1-6 alkylamino, di(C 1-6 alkyl)amino, oxo, C 1-6 alkyl, hydroxyl C 1-6 alkyl, halo C 1-6 1 alkyl and C 1-6 alkoxyl, wherein the number of the substituent is 1 to 4; R 5 is -Q-R 8, Q is selected from methylene and ethylene, R 8 is selected from the group consisting of phenyl, 8 to 9 membered fused cyclyl and 8 to 9 fused heterocyclyl; each optionally substituted with substituent L 5, said substituent L 5 is selected from the group consisting of fluoro, chloro, methyl, trifluoromethyl, methoxyl, ethoxyl, trifluoromethoxyl, dimethylamino and carboxylmethyl, wherein the number of the substituent is 1 to 4; R 2 is hydrogen; R 4 is hydrogen; R 6 is hydrogen. R 1 is selected from the group consisting of 6 to 7 membered saturated N-containing fused heterocyclyl, 7 to 10 membered N-containing spiro heterocyclyl and 7 to 8 membered N-containing bridged heterocyclyl; each attached to pyrimidyl via nitrogen and optionally substituted with a substituent selected from the group consisting of halogen, cyano, amino, hydroxyl, C 1-6 alkyl, halo C 1-6 alkyl, hydroxyl C 1-6 alkyl and C 1-6 alkoxyl, wherein the number of the substituent is 1 to 4; R 3 is -M-R 7, M is selected from a single bond and C 1-6 alkylene, R 7 is selected from the group consisting of phenyl, tetrahydrofuranyl, tetrahydrothienyl, tetrahydropyrrolyl, imidazolidinyl, pyrazolidinyl, piperidinyl, morpholinyl, piperazinyl, 2-oxo-azacycloheptanyl, 2-oxo-piperazinyl, furanyl, dihydrothienyl, dihydropyrrolyl, dihydrooxazolyl, dihydropyrazolyl, thienyl, pyrrolyl, imidazolyl, thiazolyl, pyrazolyl, pyrimidyl, pyridyl, pyrazinyl, oxazolyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, naphthyl, indolyl, benzimidazolyl, 2,3-dihydrobenzfuranyl, quinolinyl, benzo[ d][1,3]- meta -dioxa-cyclopentenyl, 7 to 10 membered spiro cyclyl, 7 to 10 membered bridged cyclyl, 7 to 10 membered spiro heterocyclyl and 7 to 10 membered bridged heterocyclyl; each optionally substituted with substituent L 2, said substituents L 2 is selected from the group consisting of halogen, hydroxyl, cyano, amino, C 1-6 alkylamino, di(C 1-6 alkyl)amino, oxo, C 1-6 alkyl, hydroxyl C 1-6 alkyl, halo C 1-6 1 alkyl and C 1-6 alkoxyl, wherein the number of the substituent is 1 to 4; R 5 is -Q-R 8, Q is selected from methylene and ethylene, R 8 is selected from the group consisting of phenyl, 8 to 9 membered fused cyclyl and 8 to 9 fused heterocyclyl; each optionally substituted with substituent L 5, said substituent L 5 is selected from the group consisting of fluoro, chloro, methyl, trifluoromethyl, methoxyl, ethoxyl, trifluoromethoxyl, dimethylamino and carboxylmethyl, wherein the number of the substituent is 1 to 4; R 2 is hydrogen; R 4 is hydrogen; R 6 is hydrogen.