This work is part of a new approach to the study of the planning of public transport in order to optimize accessibility by these means of travel in the Greater Skikda (Northeast Algerian). Isochronal indicators are used to measure spatial-temporal accessibility, an approach based on the use of new information technologies as a tool for analysis, such as Geographic Information Systems (GIS). Since the 1970s, the city of Skikda has experienced an urban dynamic, mainly due to high population growth, rural exodus and a number of other social, economic factors. This rapid urbanization has plunged the city into a multidimensional crisis, generating a multitude of problems: urban congestion, transport problem, environmental degradation, poor space management, etc. In addition to these factors, the centralization of commercial and administrative activities in the city, generate a lot of mobility by creating a large daily flow of travel. In this context public transit by bus should be the appropriate solution to facilitate mobility in the city and minimize road congestion. In this paper we analyzed the level of spatial-temporal accessibility by public transport and drew up a mapping that could be an effective tool for assisting local actors in decision-making in organizing the transport network and optimizing its performance.