数字电视指将传统的模拟信号转化为数字进行处理、传输和接收的系统。数字电视的条件接收系统运用各种数字技术通过对节目的加扰处理,使只有授权用户才能收看被加扰节目,从而保障运营商的利益,保证数字电视发展。本文主要阐述当前数字电视使用的条件接收系统的基本原理,以及实际中应用两种条件接收方式的设计和实现,并比较两种方式的优势和不足。最后介绍当前国内数字电视发展的现状。 Digital television refers to the traditional analog signals into digital processing, transmission and reception system. The digital TV conditional access system uses various digital technologies to scramble the programs so that only authorized users can watch the scrambled programs so as to protect the interests of the carriers and ensure the development of the digital television. This article mainly expounds the basic principle of the conditional access system used by the current digital television and the design and implementation of the two reception methods in practice, and compares the advantages and disadvantages of the two methods. At last, we introduce the current situation of digital television in China.