Automated　cell　immobilization　is　a　key　technology　in　robotic　single　cell　manipulation.　In　the　existing　automation　methods　of　cell　immobilization,　the　microinjection　tools　(microgripper　or　micropipette)　and　the　cells　need　to　be　manually　put　into　the　culture　media,　and　then　the　microgripper　or　micropipette　is　automated　to　gradually　approach　the　plane　in　which　the　center　of　the　cell　is　located　in　order　to　clamp　or　adsorb　the　cells　to　immobilize　cell.　This　paper　presents　a　novel　technology　that　is　capable　of　automatically　moving　down　the　gripper　into　the　culture　media　from　the　outside　air　environment,　and　then　precisely　clamping　a　cell　in　the　liquid　environment　for　injection.　In　the　proposed　solution,　an　active　window-based　auto-focusing　algorithm　is　developed　to　solve　the　challenging　problem:　the　image　information　is　lost　due　to　the　＇viscous　effect＇　taking　place　when　the　gripper　jaw　touches　the　water　surface　and　enters　the　culture　media.　The　proposed　algorithm　are　tested　and　validated　by　the　immobilization　experiments　of　zebrafish　embryos　using　the　in-house　develop　micro-robotic　system.　The　proposed　algorithm　in　this　paper　can　help　firmly　immobilize　cells,　significantly　improve　the　automation　of　micromanipulation,　and　reduce　the　working　intensity　of　the　labors.　©　2019　IEEE.