The invention discloses a mixed flow non-sunken bioretention pond having an initial rainwater discarding function. The retention pond comprises a bottom and sidewalls, and the retention pond is composed of three parts, namely an initial rainwater discarding and distributing well (10), a retention pond main body (20) and overflow and outflow water collecting well (30). Effective discarding and separating of initial rainwater can be achieved, and runoff pollution can be effectively controlled; a requirement on sinking downwards can be avoided, particulate pollutants in runoff entering facilitiescan be effectively relieved, the possibility that the bioretention pond gets blocked can be obviously reduced and efficient running of the facilities for a long term can be guaranteed; and through amixed flow mode combining 'upwards flowing and downwards flowing', overflowing paths of the runoff in the facilities are increased, and a control effect of the facilities over runoff pollution is obviously improved.