Is there any free source of Digital elevation model of China with the resolution of 30 meters or better and vertical accuracy of +-5m. Something along those lines
SRTM at 1-arc second resolution has been published for this area. The spatial resolution is approximately 30m. Vertical accuracy is generally within your limits but, like any SAR DEM, varies with topography and land cover.
You can search and download them from USGS EarthExplorer (Data Sets -> Digital Elevation -> SRTM).