Rotary cushion valve, rotary hydraulic system and engineering machine

The invention provides a rotary cushion valve, a rotary hydraulic system and an engineering machine. The rotary cushion valve comprises a pilot overflow valve. The pilot overflow valve comprises a main valve and a pilot valve, a delay decompression device is arranged on a pilot oil passage from the main valve to the pilot valve, and pressure change of a spring cavity can lag under the effect of the delay decompression device. The rotary cushion valve, the rotary hydraulic system and the engineering machine have the advantages that the delay decompression device which comprises components such as a damping hole and an elastic container is arranged on the pilot oil passage of the pilot overflow valve of the rotary cushion valve, a decompression procedure of the main valve of the pilot overflow valve can be delayed under a delay effect of the damping hole or a volume effect of the elastic container, accordingly, the rotary cushion valve can be started when impacted, the problem that an existing overflow valve (at a high setting pressure) cannot be started when impacted at a low pressure in a rotary procedure can be solved, and a rotary cushion effect can be effectively realized.