Abstract: It is required to unload the closing and opening chambers of blowout preventers before repairing or replacing the rams and rubber seals of blowout preventers. The conventional three-position four-way rotary valve suffers from complex operation, waste of pressure, wear of valves and the disadvantage that all controlled components cannot be remotely operated after pressure relief of pipes. Given this, the four-position four-way rotary valve was developed. An extra oil unloading path was designed for the valve body and element, respectively to change the original valve into a four-position four-way rotary valve capable of automated pressure relief. In practice, it is required to only switch the valve handle to the unloading position to separately depressurize the repair target while maintaining the pressure in the rest pipes. All the other controlled components, except for those to be repaired, are under remote hydraulic control. The invention simplifies operations of repairing and replacing blowout preventer rams and rubber seals, reduces their energy consumption and improves their efficiency. The presented design also decreases the wear of valves attributed to repeated switching and greatly enhances operational efficiency.