Engine system and all-terrain vehicle

An engine system, comprising:

• an engine, which comprises a housing and a crankshaft part, wherein the housing is provided with an accommodating cavity, the crankshaft part is provided in the accommodating cavity and is configured to output first power, and an output end of the crankshaft part for outputting the first power extends out of the accommodating cavity;
• a first motor, which is located outside the accommodating cavity and provided on the housing, wherein the first motor comprises a first motor shaft, and the first motor shaft is connected to the output end of the crankshaft part to convert the first power into electric energy;
• a second motor, which is located outside the accommodating cavity and provided on the housing, wherein the second motor comprises a second motor shaft and is configured to output second power according to electric energy;
• a speed change mechanism, which is provided in the accommodating cavity and drivingly connected to the second motor shaft without connecting to the output end of the crankshaft part, and is configured to perform speed change processing on the second power to output third power;
• and
• a transmission shaft, which is provided in the accommodating cavity and connected to an output end of the speed change mechanism for outputting the third power, and is configured to output fourth power.