The present disclosure provides a method and an apparatus for obtaining an expression from characters. The method may include: extracting N words under test from a text under test in an arrangement order; inputting an i-th node in the first-level operation, each node of a first node to an i−1 th node in the first-level operation, and a predefined set of operators into a sub-network of a recurrent neural network to obtain nodes of a second-level operation; determining a valid operator in the first-level operation according to the nodes of the second-level operation; performing multi-level operations until the number of valid operators in a M-level operation is determined to be 0 according to the obtained nodes of the M+1-level operation; and generating the expression from the text under test according to valid operators in the first-level operation to the M−1-level operation and words corresponding to valid nodes.