Due to a strong competition between other groups doing muSR study, we are submitting this proposal as a Rapid proposal. Recently, Wang et al. found the first nitrogen-containing superconductor ThFeAsN with Tc=30K. This new superconductor belongs to the 1111 family of FeAs-based superconductors. The aim of the proposed experiment is to use muSR to investigate the nature of superconducting state of ThFeAsN and to further explore the normal state properties, which will be of interest for ongoing research in the field of Fe-based superconductivity. µSR studies are important for investigating the microscopic field distribution inside a superconductor. Furthermore, µSR studies will provide direct information about the pairing symmetry or symmetry of the order parameter and gap structure in ThFeAsN, which is important for understanding the multiband superconductivity in Fe-based systems.