Musical experience has been found to aid speech perception. This electroencephalography study further examined whether and how musical expertise affects high-level predictive semantic processing in speech comprehension. Musicians and non-musicians listened to semantically strongly/weakly constraining sentences, with each sentence being primed by a congruent/incongruent sentence-prosody. At the target nouns, a N400 reduction effect (strongly vs. weakly constraining) was observed in both groups, with the onset-latency of this effect being delayed for incongruent (vs. congruent) priming. At the transitive verbs preceding these target nouns, musicians' event-related-potential amplitude (in incongruent-priming) and beta-band oscillatory power (in congruent- and incongruent-priming) showed a semantic-constraint effect, and were correlated with the predictability of incoming nouns; non-musicians only demonstrated an event-related-potential semantic-constraint effect, which was correlated with the predictability of current verbs. These results indicate musical expertise enhances semantic prediction tendency in speech comprehension, and this effect might be not just an aftereffect of facilitated acoustic/phonological processing.