为了实现微米级物体快速、高精度位置测量，弥补传统利用CCD 成像直接探测法的不足，采用后焦面法实现了光阱环境中微粒小球的位置探测。阐述了后焦面法位置探测的基本原理和实现方法，并搭建实验光路，实现了模拟光阱环境中微米小球位置的快速精确测量。理论分析及实验结果表明：这种方法位置探测分辨率可达80 nm、响应频率达到800 Hz，将其用于光阱环境中微米小球的位置探测是切实可行的。

In order to make up for the disadvantages of traditional CCD method and monitor particle′s position quickly and high precisely, back-focal-plane (BFP) method is used to detect the particle′s position in an optical trap. The basic principle of BFP method for position detection is explained, then the experimental system is built and the target that detect the particle′s position quickly and high precisely is achieved. The experimental result shows that the detection accuracy reaches 80 nm and the response frequency reaches 800 Hz，so it can be used to detect the micro particle′s position in an optical trap.