For the problem of short communication distance in continuous-variable quantum key distribution (CVQKD) protocol and on the basis of multidimensional reconciliation scheme, the low-density parity-check (LDPC) codes with good degree distribution are designed using a continuous density evolution and differential evolution method. The method of repeating LDPC codes is proposed as well, which further improves the efficiency of multidimensional data coordination, effectively reduces the convergence signal-to-noise ratio threshold and extends the secure range of communication distance. The simulation results indicate that when the block length is 106, the convergence signal-to-noise ratio can be less than -6 dB, and the data reconciliation efficiency can achieve 90.27%. The amount of the extracted secure secret key is about 0.22 kb/s, and the secure range of communication distance exceeds to 80 km, which means the distance can be effectively extended in CVQKD system.