6 yrs boy have tumour in one testicle, is there any other way without removing whole testicle, if the tumour is not carcinogenic?

Ask his urologist: An ultrasound of the testis can give us a pretty good idea about the nature of this tumor. If it is suspicious for malignancy then there is no chance to save his involved testicle. Otherwise the swelling can be monitored for 1-2 months and watch for increase in size(further growth of the tumor) which would imply that this tumor is likely malignant.

Possible, but...: Most of testicular tumors at 6 are benign, but radical orchiectomy remains the procedure of choice. But if alpha-fetoprotein is negative and the findings of physical and ultrasound exam strongly suggest benign, masses, tumor excision alone can be done through inguinal incision with help of intra-operative pathological frozen section by an experienced surgeon. So, talk and work with experts.