Food-chain length (FCL)is a significant ecosystem index. It can influence the biodiversity, pattern and stability of the biological community by altering trophic interactions within it. Food chains are caricatures of communities that trace linear either energy or the effect strength pathways from primary producers to apex predators embedded within more complex food webs. And Food chains are also the basis for many important concepts in ecology. In the last few years, innovative process-level studies have been expanding rapidly. Food chain length theory to ecological research is becoming increasing common and to significant new levels of understanding of ecological processes and elemental fluxes through biological and abiotic systems. Food webs represent a road map of feeding relationships in ecological community and can be defined in at least three different ways. we defined three commonly used operational definitions of FCL and reviewed the method measuring of the three kind of food chain length including the characteristics. Conventional wisdom holds that either resource availability or disturbance limit food-chain length; however, new researches and new techniques challenge the conventional wisdom and broaden the discourse on food-chain length. We reviewed four hypotheses on the determinant of FCL including resource availability hypothesis, productivity space hypothesis, ecosystem size hypothesis and dynamic stability hypothesis and the relation among these hypotheses. In this article, we discussed the evidence for controls on FCL in freshwater ecosystems. Recent results suggest that resource availability limits food-chain length only in system that the resource availability is very low. Different defines of ecosystem size can cause different result about the ecosystem size hypothesis. And ecosystem size controls food chain length only at local region, while at the global pattern the relationship between ecosystem size and food chain length is very weak. The independence and interaction between four hypotheses indicate the complexity and diversity of food chain length controls in ecosystems. Food-web structure is closely relevant to the functioning of ecosystems. We further synthesized the spatial pattern and determinants of FCL in lake ecosytems as a empirical complementation to the theoretical study. So the factors that control or alter food webs are more and more considered in managing, conserving, and restoring aquatic ecosystems. At the last part of this study, we reviewed the problems in the recent research on this issue and looked into the meaningful research in the future including movement of contaminants, biomanipulation, and climate change, several important areas of use of basic food-web research in applied issues.