In this paper, a new method of simulating monthly mean temperature in county-size mountainous areas is presented. Taking Longquan county, Zhe-jiang province as an example, some simulating formulate are obtained from experimental data. The climagraphes drawn according to these calculated data of monthly, annual mean temperature and various agricultural index temperatures can reflect the effection of topogragphy in more details and then is more valuable to indicating the distribution of heat resource.