In WSN(Wireless Ad-hoc Sensor Network)

some sensor nodes could die with their limited power consuming

which leads to the decrease of the point covering quality.Thus a method must be found to evaluate the quality of nodes' covering.An evaluating algorithm is proposed to measure how well a set of object points are monitored by sensor networks on the basis of Monte Carlo algorithm.The algorithm evaluates some points which are randomly selected from the set of object points.If all selected points meet the requirement

it will return;or it demarcate those object points which don't meet requirements.Repeat to call the algorithm limited times

which will make the ratios of the correctness of the quality evaluation algorithm exceed 99%.So it solves point covering problem effectively in WSN.The simulation shows that it is feasible.