The expansion of two different kinds of hydrodynamic size of polymethyl methacrylate (PMMA Mw: 1.56- 2.04 ${ imes}$ 106 g/mol) has been measured by dynamic light scattering and viscometry above the Flory $ heta$ temperature of the variou s solvents such as n-butyl chloride, 3-heptanone, and 4-heptanone. The expansion of PMMA chains was analyzed in terms of universal temperature parameters and also compared with previous results of polystyrene (PS) system. First it was found that simple $ au/{ au}c$ parameter no longer had its universality for the expansion behavior of hydrodynamic size in the chemically different linear polymer chains. However after modifying ${ au}/{ au}c$ parameter into $(Mw/Ro2)3}2( au/ auc)$, we observed a much better universality for both PMMA and PS systems. Here Mw, Ro, $ au[=(T-{ heta}$)/${ heta}$]$</TEX>, and ${ au}c[=({ heta}-Tc)/Tc]$ are defined as the weight average molecular weight, the unperturbed end-to-end distance, the reduced temperature and the reduced critical temperature, respectively.