A menstrual cup device and a method of us thereof includes a menstrual cup made of expandable material so as to be compressed, the menstrual cup having resilience for restoring to its original shape after being compressed, the menstrual cup comprising a pulling stem at a lower end thereof, a circular lip at an open upper end thereof, and a circular groove below the circular lip; and a collection bag having a resilient restraining ring at an open upper end thereof; thereby, the resilient restraining ring being expanded to be constricted in the circular groove of the menstrual cup, the circular lip being adapted to prevent the resilient restraining ring from disengagement, the menstrual cup with the collection bag being compressed and inserted into the vagina for collecting menstrual blood, the collection bag being disposable and replaceable.