The additional stress which is caused either by air pressure and rain fall (The phenomena are defined as air pressure effect and rain effect respectively), or by rise and fall of surface water (such as river, lake etc.) can disturb water level of pressure well. In this paper, the solution of elastic half-space is used to analyse the pressure effect and rain effect. The pressure coefficient by J. Bear is modified and meanwhile the rain coefficient is proposed. Through calculation, we find that air pressure coefficient and rain coefficient are related not only to the behavior of aquifer, but also to the range of pressure variation, area of raining and the depth of pressure aquifer. Some facts of observation have been proposed that the sum of the two coefficients equals unity which is also proved in this paper. Taking Su-07 well as an example, we analyse the disturbance caused by rise and fall of the surface water, and the results of calculation is nearly keeping with the results which are got from the calculation of regression analysis.