A child safety seat assembly includes a base having two fixed anchoring hooks, a seat shell detachably installed with the base, two catching collars pivotally assembled with the seat shell, the collars being operable to respectively engage with the anchoring hooks to hold the seat shell with the base, and a release actuator operatively connected with the catching collars, the release actuator being operable to rotate the catching collars to disengage the catching collars from the anchoring hooks.