The excessive speed of development for tourism seriously restricts the sustainable development of ecological conservation areas (ECAs). In this study, we take Beijing's ecological conservation area (BECA) as the study area, and construct the model of the green development level of tourism (GDLT) in ECAs to measure and analyze the spatial–temporal evolution and factors influencing of GDLT in BECA. Our results demonstrate that the GDLT in BECA continued to rise from 2011 to 2017, but the spatial distribution was unbalanced. The main factors influencing GDLT in BECA have been the endowment level of green tourism resources and the construction level of the regional ecological civilization. The new method to measure GDLT in ECAs presented here can provide reference for the green development of tourism in ECAs. The findings can construct the theory of the green development of tourism in ECAs, and enrich the theory of tourism geography and tourism ecology from the perspective of the green development concept.