In order to solve the problem of larger pattern jitter in Gardner timing synchronization loop

various pattern jitter reduction algorithms existing are classified and researched

which are divided into two categories of modification and waveform pretreatment of algorithms. With the modified Cramer-Rao bound（MCRB） as a criteria for judging the quality of researched algorithms

these algorithms are separately analyzed from the S curve characteristics and timing jitter variance in theory and simulation. Finally

the actual application scenes of various algorithms and future research directions are simply summarized.