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Phase transition is a popular phenomena in nature,among them the transition from normal fluid to superfluid for helium is a famous one,since many abnormal phenomena appear around the transition point,one of them is the Lambda point,while the temperature below it the normal fluid helium(helium Ⅰ)would take transition to superfluid helium Ⅱ.The achievement of Bose-Einstein Condensation open a new field to the scientists,it has many similar properties as same as the helium liquid.There is also the Lambda phase transition point for Bose gas,while the temperature below the critical temperature,the normal Bose gas would take transition to quantum gas,which behaves as superfluid.There are many ways to measure the phase transitions,such as BEC profile with bimode,interference of superfluid to Mott insulator in 1D optical lattice.We proposed some new methods to measure the behavior of phase transition of Bose Condensate and Bose Condensate in 1 D optical lattice.First,we demonstrate to measure the correlation length in phase of superfluid and Mott insulator in 1D optical lattice by means of Superradiant Rayleigh scattering [1].The correlation length shows the phase transition of superfluid and Mott insulator in 1D optical lattice.Second,we report the results of a study of measuring the correlation length at the Lambda critical phase transition point in an ultra-cold Bose gas with a temporal Talbot-Lau(TL)interferometery [2].We demonstrate a new approach,a temporal Talbot-Lau(TL)interferometer,to measure correlation length.The whole correlation length cure at the Lambda critical phase transition point can be measured in an ultra-cold Bose gas with a temporal Talbot-Lau(TL)interferometer[3],and the critical exponent factors for the curve are also measured,which is equal to the universal value in quantum gas,0.67.