We presented a lattice-QCD calculation of dibaryon matrix elements with weak current insertions by using point-splitting interpolating field operators. Our method of calculating two-point, three-point and four-point correlation functions is described in detail and we make a comparison between the correlation functions obtained from our point-splitting operators and point operators and report the preliminary results. We found that the excited-state contamination is reduced by using point-splitting operators and our lattice result of proton axial charge is consistent with the results from RBC/UKQCD collaborations and the matrix elements of proton-proton fusion and double beta decay agree with the results from NPLQCD collaboration.