Abstract: From the well-known fact that the solar hard X-rays are produced by an energetic electron beam impinging on solar atmosphere, and based on the observational fact that there are good correlation between the solar hard X-ray flux and energy spectrum, in this paper, a source function with synchronous variation between the injecting electron beam flux and spectrum index is proposed, and some calculating results about hard X-ray temporal properties in solar flares are obtained. These results show: high energy delay and emission broadening are two manifestations of solar hard X-ray temporal properties in the nonthermal bremsstrahlung process, and the relation between them is very dominant. The lower the density of solar atmosphere where hard X-rays produced, the more distinct for high energy delay and emission broadening of solar hard X-rays.