Gravitational waves from binary black hole merger leave permanent imprint on space-time, called gravitational wave memory. In this talk I will discuss the property, detection scheme, waveform template and the stochastic background due to gravitational wave memory. Due to the quasi-direct current behavior and the weakness of the gravitational wave memory, it is hard for waveform analysis method to detect gravitational wave memory. We implement a completely different scheme in a recent work to measure gravitational wave memory. We found 4 golden gravitational wave events in LIGO O1/O2/O3a data whose gravitational wave memory can be measured quite well. Amounts of memory events can form a “stochastic gravitational wave memory background” (SGWMB) which has not been investigated before. We find that SGWMB can be described as a Brownian motion. The power spectral density (PSD) of SGWMB corresponding to a set of binary black hole coalescence is proportional to 1 over f-squre where f is the frequency of the background. I will give some clue that SGWMB can provide a brand new mean to detect gravitational wave memory and it opens a new window to explore the gravity theory.