The invention discloses a parallel hierarchical decoder for a low density parity code (LDPC) in a mobile digital multimedia broadcasting system. The parallel hierarchical decoder adopts a partially parallel structure and is characterized in that: 1) each line of a check matrix is taken as a layer, check nodes of each layer are updated sequentially for each variable node, the variable node is updated after the check nodes of each layer are updated and a value obtained after updating is used in the updating of the check nodes of a next layer until an iteration is finished; and 2) the check nodes of a plurality of lines are selected for parallel computation under the condition that 1) is met, so that a partially parallel decoding structure can be realized. Compared with the conventional LDPC decoder, the parallel hierarchical decoder has the advantages of reducing average iteration times needed when a decoding convergence condition [bit error rate (BER) is less than or equal to 10 to 6] is met under the condition of the same signal to noise ratio and the same maximum iteration time, achieving higher error code performance, greatly increasing decoding throughput rate or effectively reducing power consumption and improving the error code performance of a system.