The application discloses a processing node, a computer system and a method for affair conflict detection. The processing node comprises a processing unit and an affair cache. When the processing unit acquires an instruction to access affairs which share data, the processing unit will access the affair cache according to the operation instruction, wherein the affair cache is used to cache the shared data of the affair which is being processed by the processing node, and the shared data is data which can be accessed by the processing node and other processing nodes. If the affair cache determines that the operation instruction misses a cache line in the affair cache, the affair cache will send a destination address in the operation instruction to affair caches in other processing nodes and will receive state information of the cache line hit by the destination address and returned by the affair caches in the other processing nodes. In this way, the affair cache can determine whether the operation instruction has conflicts with the operation instructions which are being executed by the other processing nodes according to the received state information.