Based on a weak reflection Bragg grating, a new distributed temperature sensing network is proposed by combining Wavelength Division Multiplexing (WDM) with Optical Time-domain Reflectometry (OTDR). WDM technology is used to enhance the FBG multiplexing capacity, and OTDR is used for each weak grating for real-time detection, so as to realize the intensive serial multiplexed grating and improve the spatial resolution. Using the tunable pulsed laser as the light source, multiple groups of different center wavelength grating are engraved in weak isometric in one fiber. Reflectivity of three groups is 3%. The center wavelengths are 1 544.660 nm, 1 545.802 nm and 1 546.900 nm three FBG, divided into three groups. In one fiber, quasi-distributed measurement is realized. Experimental results show that, in 5~80℃ temperature range, FBG center wavelength with temperature change shows good linearity, linearity reaching more than 99.6%, the temperature measurement resolution of up to 0.11℃, a spatial resolution of 2 m.