中文摘要：

OTF（On-The-Fly）观测模式是目前单天线最有效的谱线成图观测技术,广泛应用于单天线的谱线成图观测。主要介绍OTF观测模式在天马望远镜的实现情况。首先介绍天马望远镜OTF观测模式的观测过程和基本观测参数;接着分别对天马望远镜OTF观测系统的结构、观测控制软件、DIBAS（Digital Backend System）谱线终端、中频传输系统以及数据预处理软件进行介绍;最后给出对W3区域中的6条氢复合线的试观测结果。目前,天马望远镜的OTF观测系统已完成多次对外开放的谱线成图观测,均取得较好的观测结果,验证了该系统的有效性。

英文摘要：

The On-The-Fly（OTF） observing mode is the most efficient spectral line imaging technique, which is widely used to perform mapping observations with the single-dish telescopes. The implementation of the OTF mode in the Tian Ma telescope is described in this paper. The specific contents are as follows. Firstly, the OTF observing process and parameters are introduced. Secondly, the system architecture of the OTF observing system, the control software, the DIBAS（Digital Backend System） spectral line backend,the Intermediate Frequency transmission system, and the data pre-reduction algorithm are described. Finally, the six hydrogen recombination lines of the W3 region are presented. At present, the OTF observing system has completed several opening observations, and these observations have obtained good results which verify the OTF system.