The invention belongs to the field of machining, and specifically relates to a machining system and a machining method for machining outer circles of mounting positions of bearings at two ends of a differential shell and a cambered surface of a mounting ball of a gear in the differential shell. The machining system of the automobile differential shell mainly comprises a lathe for machining the outer circles of the mounting positions of the bearings at the two ends of the differential shell, a lathe for machining the cambered surface of the mounting ball of the gear in the differential shell and a control system, wherein the lathe for machining the outer circles of the mounting positions of the bearings at the two ends of the differential shell comprises a first body, a main shaft, a pneumatic tailstock and a first tool; the lathe for machining the cambered surface of the mounting ball of the gear in the differential shell comprises a second body, a left power head, a right power head, a positioning and clamping device and a tool changing device. According to the system and the method, the machining accuracy and the machining efficiency are improved, the rejection rate is greatly reduced, and the problem of high difficulty in machining of the outer circles of the mounting positions of the bearings at the two ends of the differential shell and the cambered surface of the mounting ball of the gear in the differential shell commonly existing in the conventional modes is effectively solved.