Abstract: In this paper, the edge effect of the heat flux plate was examined and the measuring accuracy of the Japanese heat flux plate, TYPE CN-81, and Australian ones was analysed with method developed from the Philip’s theory.The output values from heat flux plates buried in various depths and in different types of soil in Geermu region were measured in the period of the Meteorological Experiment on the Qinghai-Xizang plateau during May-August, 1979, and a harmonic wave analysis of these results was made. Reasonability of time structure and space structure of the heat flux waves was examined according to heat diffusion equation. It showed that if the instrument constant of heat flux plates was assumed as a fixed value, the variation of the phases and the amplitudes of the heat flux waves measured by heat flux plates with depth is reasonable, but the absolute amplitude values contain error, for example, the measured mean values of the heat flux is about 14% lower in the meadow-saline soil, and about 1/3 lower in the gobi in Geermu region.