Recent work proposes Cross-Technology Communication (CTC) from IEEE 802.11b to LoRa but has a low efficiency due to the extremely asymmetric data rates. In this paper, we propose WiRa that emulates LoRa waveform with IEEE 802.11ax. By taking advantage of the OFDMA in 802.11ax, WiRa uses only a small Resource Unit (RU) to emulate LoRa chirps and sets other RUs free for high-rate WiFi users. WiRa carefully selects the RU and adopts WiFi frame aggregation to emulate the long LoRa frame. We propose a subframe header mapping method to identify and remove invalid symbols caused by irremovable subframe headers in the aggregated frame. We also propose a mode flipping method to solve Cyclic Prefix (CP) errors, based on our finding that different CP modes have different impacts on the LoRa symbol. To cope with channel dynamics, we design an adaptation mechanism to maximize the goodput with a satisfying SER. We further extend WiRa to one-to-many transmission scenario by concurrently emulating LoRa chirps in different RUs. We implement a prototype of WiRa on the USRP platform and commodity LoRa device. Experiments demonstrate WiRa can efficiently transmit complete LoRa frames with the throughput of 40.037kbps and the SER lower than 0.1.