The invention discloses an online checking method of parallel computing in an electrical power system. The method comprises the following steps of (1) building a Hadoop environment; (2) initializing Hadoop-based online check tasks; (3) deposing the online check tasks; (4) executing the online check tasks in parallel; (5) combining and computing each online check task. Due to the fact that Hadoop, i.e. a software frame which can process a large amount of data in a distributing way, is applied to online check of parallel computing in the electrical power system, the problem that too much time is used for large data numerical computing is solved, and the speed of online check computing is greatly increased.