To solve the problem that quasicyclic lowdensity paritycheck (QCLDPC) codes cannot be flexibly selected, a cyclicshift matrix based on da yan sequences was used to extend the protograph basic matrix, and a novel method was constructecd for multirate QCLDPC codes. The method uses computer searching algorithm to obtain the protograph basic matrix, and then applies cyclicshift matrix to extend it to obtain the check matrix. The check matrix constructed by this method has a girth of at least 6, and only a simple shift register is needed to achieve coding, and a good error correction performance is realzied. Simulation results show that the constructed PDYQCLDPC(4000, 2000) code with the coderate of 0.5 and PDYQCLDPC(4000, 3000) code with the coderate of 0.75, compared with other codes with the same coderate and approximate codelength, both can improve the net coding gain at the bit error rate of 10-6.