The invention discloses a separated crankshaft of a four-cylinder four-stroke internal combustion engine and relates to the field of internal combustion engines. The problems of current internal combustion engines that the machining difficulty is high, the abrasion is prone to occur, and the energy consumption is high are solved. A crankshaft connecting rod device of the separated crankshaft of the internal combustion engine comprises a crankshaft, a connecting rod and a crankshaft gear. A lubricating device is provided with a lubricating oil tank bottom board; a balance block end of the crankshaft is fixedly connected with the crankshaft gear; a crankshaft connecting rod handle of the other end which is opposite to the end with a balance block of the crankshaft is connected with the connecting rod in a sleeve mode; four crankshaft gears are arranged on a directional change gear of an output power shaft at equal intervals; the connecting rod is movably connected with a piston through an anti-eccentric device. The separated crankshaft of the four-cylinder four-stroke internal combustion engine is simple in structure, easy to manufacture, small in size, high in accuracy and durable.