Data collection is the most crucial problem of wireless monitoring networks. The UAV based data collection methods have become the trend, as they can reduce the relaying times of data from the source to the sink, and improve the efficiency of network energy by replacing traditional self-organized transmission nodes with UAV. Current UAV based data collection schemes, however, focus on how to maximize the quantity of data using limited energy without consideration of data value, and hence perform poorly in energy efficiency of UAV. The challenge for achieving maximum data value with minimum UAV energy consumption is to measure the value of the data, as the value of data is subjective evaluation of applications, and there is no uniform measurement to compare the value of data that collected by different nodes. This paper introduces the first data value based data collection method OnValueGet that collect the most valuable data under the energy constraint. The intuition underlying the design is that nodes with similar data experience similar data value. The paper defines and selects the most valuable nodes(called data-critical nodes) by analyzing and comparing the temporal and spatial similarity of data. The data sensed by data-critical nodes can approximately represent all nodes' sensing data within a certain error. Aiming to collect the data of these data-critical nodes, the paper then adapts greedy algorithm to programing the route of UAV with the limited energy, and significantly improves the energy efficiency.