The relationship between wavelength demand and network physical connectivity is studied to solve the wavelength resource shortage problems in dynamic optical satellite network, and a method based on a time-space conflict map is proposed to analyze the characteristics of wavelength resources. The method for randomly generating network topology connections is utilized to discretize the dynamic topology of an optical satellite network into a space conflict map and a time conflict map, which express the physical connectivity and effective service window of the optical satellite network, respectively. Based on the time-space conflict map theory, the path selection probability of space conflict avoidance and the effective window service probability of time storage are established and multiplied to obtain the conflict probability in time-space and calculate the number of wavelengths required in the network. The results show that wavelength requirements are closely related to the network physical connectivity, maximum number of link hops, and number of transponders. More wavelength resources should be allocated to an optical satellite network with a larger business overlap factor.