Quaternionic Hilbert space has received great attention in the research of quantum physics. The duality and sum of frames are hot issues in frame theory.In this paper,We firstly introduce the notion of pre-frame operators on frames in Q-Hilbert spaces, and characterize Hilbert(orthonormal) bases,frames, dual frames and Riesz bases, and obtain the accurate expressions of all dual frames of a given frame by taking advantage of pre-frame operators.We also characterize the dual frames through an operator equation. Secondly,we discuss sums of frames with the help of the pre-frame operators, and gain some more general methods to construct new frames. Moreover, we obtain a necessary and sufficient condition for the finite sum of frames to be a (tight) frame.