Abstract: Implementations of the subject matter described herein provide a solution for speech synthesis and speech recognition. In this solution, a Text to Speech (TTS) model and an Automatic Speech Recognition (ASR) model supporting at least one language are obtained. The TTS model and the ASR model are adjusted, based on a first set of paired data in a target language, to support the target language. The TTS model is optimized based on the first set of paired data and a first set of synthesized paired data in the target language generated by the ASR model while the ASR model is optimized based on the first set of paired data and a second set of synthesized paired data in the target language generated by the TTS model. As such, the solution can provide TTS and ASR models with high accuracy for languages lacking training data by using less training data.