An emerging two-dimensional (2D) tungsten disulfide (WS2) has been attracting much attention due to its excellent physical properties. In this work, the thermal transports in isotopically doped WS2 monolayers modified with Rectangle Carpet (RC) and Sierpinski Carpet (SC) structures are investigated systematically using molecular dynamics simulations. The effects of fractal number and temperature on thermal conductivity (k) are evaluated. The SC fractal structures have lower thermal conductivities in comparison with the RC structures for each fractal number. Furthermore, an initial decreasing and then increasing trend of k is observed with increasing fractal number. We can also observe a negative correlation between k and temperature. The phonon dispersion, group velocity, participation ratio, spatial distribution of energy and phonon density of states are evaluated to reveal the thermal transport mechanism in WS2 monolayers. This work provides valuable information on phonon behavior to tune the thermal transport in 2D WS2 monolayers based thermoelectric applications.