Improving the frequency-temperature characteristic of widely used rubidium clocks is an important topic of research. Through studying the frequency locking principle and frequency-temperature characteristic of rubidium clock, we put forward a method for improving its frequency-temperature characteristic based on frequency compensation technique; the operation principle, circuit implementation, signal processing method and optimal control method for the frequency conversion process are studied emphatically. The experiment on a commercial rubidium clock was conducted, and the experiment result was also studied. The experiment result shows that with the proposed approach, the frequency-temperature characteristic of the commercial rubidium clock is improved dramatically without deteriorating the other clock performance indexes. Compared with the traditional methods that optimize the atomic clock physical design or enhance the stability of the clock temperature control circuit, the proposed method has the advantages, such as easy realization, high stability, high precision, easy to adjust, and etc.