The invention discloses an M65-grade electric resistance welding casing pipe and a manufacturing method thereof. The M65-grade electric resistance welding casing pipe comprises, by weight percentage, 0.14-0.18% of C, 0.15-0.30% of Si, 1.10-1.40% of Mn, less than or equal to 0.020% of P, less than or equal to 0.008% of S, 0.06-0.12% of Ti, 0.02-0.05% of Als, less than or equal to 0.008% of N, less than or equal to 0.40% of carbon equivalents and the balance Fe and unavoidable elements. A continuous casting sheet billet is heated to 1150-1200 DEG C through a heating furnace and subjected to hot continuous rolling. The finishing rolling temperature is 780-840 DEG C. After being rolled, a steel belt is cooled at the speed of 8-12 DEG C/s. The steel belt is coiled at the temperature of 560-620 DEG C. The steel belt is subjected to high frequency/medium frequency electric resistance welding and made into a steel pipe through an ERW unit. The whole pipe is subjected to the normalizing heat treatment process, wherein the whole pipe is heated to 880-910 DEG C, the temperature is preserved for 30-50 minutes, and air cooling is conducted. The steel belt is good in weldability and impact toughness; normalizing treatment is adopted, so that banded structures and residual stress are eliminated; the heat treatment process is simplified; and performance consistency of a pipe body and weld joints is guaranteed.